Status review of the Arran endemic whitebeams, Sorbus arranensis and Sorbus pseudofennica

68 

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For further information on this report please contact:

Graeme Walker

Scottish Natural Heritage

19 Wellington Square

AYR

KA7 1EZ

Telephone: 01292 261392

E-mail: graeme.walker@snh.gov.uk

This report should be quoted as:

Robertson, A. (2004). Status review of the Arran endemic whitebeams,

Sorbus arranensis

and

Sorbus pseudofennica

. Scottish Natural Heritage Commissioned Report No. 056

(ROAME No. F03LI14).

This report, or any part of it, should not be reproduced without the permission of Scottish Natural Heritage.

This permission will not be withheld unreasonably. The views expressed by the author(s) of this report should

not be taken as the views and policies of Scottish Natural Heritage.

Commissioned Report No. 056

Status review of the Arran endemic

whitebeams,

Sorbus arranensis

and

Sorbus pseudofennica

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Background

Sorbus arranensis (Arran whitebeam) and Sorbus pseudofennica (Arran service-tree) are two endangered, endemic tree species found only on the Isle of Arran. With the exception of Salix lanata(woolly willow), they are considered to be closer to extinction than any other tree or shrub in Scotland. Studies have shown that S. arranensis is of hybrid origin from the parent species S. aucuparia (rowan) and S. rupicola (whitebeam sp.). Subsequent hybridisation of S. arranensiswith S. aucupariahas given rise to S. pseudofennica.

It has been demonstrated that the Sorbus complex(parent species and hybrid taxa) on Arran is an actively evolving entity with new genotypes being generated throughout the range of endemic taxa. To date, conservation efforts have concentrated on protecting only the hybrid taxa within the Gleann Diomhan National Nature Reserve (NNR). However, to maximise their chances of long term survival, all components of this evolutionary complex should be conserved.

Main findings

● In order to understand the dynamics of Sorbus populations more frequent surveys should be established to record factors such as seedling recruitment, reproductive potential and grazing pressure. It is important to identify a population, or a permanent sample plot within the NNR, that is not only a representative cohort of trees but is easily accessible and convenient to survey. Data can then be regularly collected in a systematic manner that will withstand changes in recording personnel.

● The progress of hybrid seedlings and saplings planted in the NNR has been monitored more closely than naturally regenerated individuals. Observations have shown that if seedlings can get established they have a good chance of survival. However, where they establish is a dominant factor in determining their form and subsequent reproductive potential. Seedlings that establish in exposed, marginal sites are likely to remain small and stunted throughout their lifetime. Climate, exposure, soil quality and the presence of large and small herbivores are the primary causes for this lack of stature.

Small and stunted trees do not appear to reproduce. Approximately 50% of the total hybrid Sorbuspopulation

are less than 1.5m high and no flowers or fruits have been observed on these individuals. Records show that many of these trees are at least 25 years old. Saplings that have established in sheltered sites are growing taller and producing flowers and fruits. Increasing the surrounding woodland cover, by planting or facilitating natural regeneration, will provide shelter with the additional benefits of improved soil quality, reduced soil erosion and a dampening of the effects of large and small herbivores through provision of additional fodder. It is possible that by being part of a larger woodland, as was the case historically, these Sorbus hybrids will be released from their annual growth and die-back cycle and begin reproducing.

Status review of the Arran endemic whitebeams,

Sorbus arranensis

and Sorbus pseudofennica

Commissioned Report No. 056 (ROAME No. F03LI14)

Contractor: Dr Ashley Robertson

S u m m a r y

For further information on this project contact:

Graeme Walker, Scottish Natural Heritage, 19 Wellington Square, Ayr KA7 1EZ. Tel: 01292 261392

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Contents

Summar y

Executive summar y

1

INTRODUCTION

1

2

OBJECTIVES

2

3

DISTRIBUTION

3

3.1

Past distribution

3

3.2

Current distribution

3

4

MORPHOLOGY

6

5

HYBRID ORIGINS

7

6

REPRODUCTION

9

6.1

Apomixis

9

6.2

Flower and fruit production

9

6.3

Vegetative reproduction

9

7

POPULATION DYNAMICS

10

7.1

Survey history

10

7.2

Population age structure

10

7.3

Natural regeneration

10

7.4

Planted seedlings

13

8

GENETIC DIVERSITY

14

9

EVOLUTIONARY POTENTIAL

16

10

DISCUSSION

17

10.1 Recommendations for site management

17

11

REFERENCES

19

Appendix 1

1997 population sur vey data

22

Appendix 2

Histor y of trees with identification tags intact

52

Appendix 3

Seedlings and young trees identified in 1997

56

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List of figures

Figure 1

Endemic Sorbus

hybrids sites (A–N) in the north of Arran

4

Figure 2

Leaf morphology of the novel Sorbus

type shown to be

8

intermediate between S. aucuparia

and S. pseudofennica

List of tables

Table 1

Locations and population sizes of endemic Sorbus

trees at

5

14 sites on Arran

Table 2a

Survey history of Arran Sorbus

hybrids in Glen Catacol and

11

Gleann Diomhan, sites A–F

Table 2b

Survey history of Arran Sorbus

hybrids in Gleann Easan

12

and Glen Lorsa, sites G–N

Table 3

Height and fate of trees in 1970, 1980/86 and 1997

14

Table 4

Number of individuals of multilocus genotypes in S. arranensis

15

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EXECUTIVE SUMMARY

Sorbus arranensis

and Sorbus pseudofennica

are two endangered, endemic tree species found only on the

Isle of Arran, Scotland. They are considered to be closer to extinction than any other tree or shrub in Scotland

(with the exception of Salix lanata). Recent studies have confirmed that S. arranensis

is of hybrid origin

from the parent species S. aucuparia

and

S. rupicola. Subsequent hybridisation of S. arranensis

with

S. aucuparia

has given rise to S. pseudofennica. An uneven age distribution and scattered occurrence of

both hybrid taxa were used as justifications for the establishment of the Gleann Diomhan National Nature

Reserve (NNR). Since the creation of this NNR, a great deal of research has been carried out on the

ecology and conservation of these trees. However, the overall picture is confused; successive surveys have

indicated an increase in population numbers although there is no clear evidence to suggest that successful

regeneration is occurring. Survey methods have not been standardised therefore the validity of comparisons

between data is questionable.

In order to understand the dynamics of Sorbus

populations more frequent surveys should be established to

record factors such as seedling recruitment, reproductive potential and grazing pressure. It is important to

identify a population, or a permanent sample plot within the NNR, that is not only a representative cohort

of trees but is easily accessible and convenient to survey. Data can then be regularly collected in

a systematic manner that will withstand changes in recording personnel.

The progress of hybrid seedlings and saplings planted in the NNR has been monitored more closely than

naturally regenerated individuals. Observations have shown that if seedlings can get established they have

a good chance of survival. However, where they establish is a dominant factor in determining their form and

subsequent reproductive potential. Seedlings that establish in exposed, marginal sites are likely to remain

small and stunted throughout their lifetime. Climate, exposure, soil quality and the presence of large and

small herbivores are the primary causes for this lack of stature.

Small and stunted trees do not appear to reproduce. Approximately 50% of the total Sorbus

hybrid

population are less than 1.5m high and no flowers or fruits have been observed on these individuals.

Records show that many of these trees are at least 25 years old. Saplings that have established in sheltered

sites are growing taller and producing flowers and fruits. Increasing the surrounding woodland, by planting

or facilitating natural regeneration, will provide shelter with the additional benefits of improving soil quality,

reduction of soil erosion and dampen the effects of large and small herbivores by provision of additional

fodder. It is possible that by being part of a larger woodland, as was the case historically, these stunted

Sorbus

hybrids will be released from their annual growth and die-back cycle and start reproducing.

It has been demonstrated that the Sorbus

complex (parent species and hybrid taxa) on Arran is an actively

evolving entity with new genotypes being generated throughout the range of the endemic taxa. To date,

conservation efforts have concentrated on protecting only the hybrid taxa within the NNR. However, to

maximise their chances of long term survival, all components of this evolutionary complex should be conserved.

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1

INTRODUCTION

In Britain, where repeated glaciation and re-colonisation has led to a depauperate angiosperm flora, a large

number of predominantly polyploidy and apomictic endemic tree taxa have been described in the genus

Sorbus

(Warburg 1938; Richards 1975; McAllister 1986; Rich and Rich 1998; Nelson-Jones et al. 2002).

They are thought to have evolved in situ

since the last glaciation (Godwin 1975; Boyd & Dickson 1987)

as a consequence of hybridisation among the sexual diploid species Sorbus aucuparia

L. (rowan), S. aria

L. Crantz (whitebeam), S. torminalis

L. Crantz (wild service-tree), and their apomictic, polyploidy derivatives

(eg S. rupicola

(Syme) Hedl. (rock whitebeam)). Two of these localised endemic taxa, S. arranensis

Hedl.

(Arran whitebeam) and S. pseudofennica

E. F. Warburg (Arran service tree), are confined to the Isle of Arran,

Scotland (Landsborough 1897; Hedland 1901; Warburg 1952). On account of their rarity they are the

only trees in Scotland in the IUCN World List of Threatened Trees and are the subject of ongoing

conservation action (Bignal 1980; Boyd et al. 1988; Robertson et al. 2004a, 2004b).

Sorbus arranensis

and

S. pseudofennica

were first described by Landsbourgh (1897) who noted the

occurrence and distribution of two kinds of cut-leafed whitebeam growing in the gorges of the north part of

Arran. For many years S. arranensis

and S. pseudofennica

were not separated taxonomically and there has

been a certain amount of taxonomic confusion: these species were classified as Pyrus pinnatifida

Sm.

(Bryce 1872) and Pyrus aria

(L.) Ehrh. (Landsborough 1897). In 1901, Hedlund described Sorbus

arranensis, but it was not until 1952 that Sorbus pseudofennica

received authoritative recognition as a

separate taxon in “Flora of the British Isles” (Clapham et al. 1952).

The stronghold of these taxa, Gleann Diomhan, was declared a National Nature Reserve (NNR) in 1956,

with a view to ensuring the long-term survival of both S. arranensis

and

S. pseudofennica. However, it is

doubtful that natural regeneration is currently adequate for the maintenance of the two species (Bignal 1980;

Boyd

et al. 1988). Since the creation of the NNR a great deal of research has been carried out on the

ecology and conservation of these trees. Surveys have indicated an increase in population numbers;

however, there is no clear evidence that successful regeneration is occurring.

Many researchers have argued that an understanding of the genetic composition of a species, or population,

is important for the construction of any comprehensive conservation plan (eg Hamrick 1983; Ennos 1991;

Falk and Holsinger 1991; Ellstrand and Elam 1993). Whereas others have expressed doubt that genetic

diversity plays a role in the survival of populations or species (Lande 1988; Schemske et al. 1994). These

latter authors argue that populations go extinct for ecological reasons (eg habitat loss or environmental

changes) rather than because they lack genetic variation. Ecological factors and demographic characteristics

of populations must play a dominant role in the short-term survival of populations and species. However, the

long-term survival of these populations must be dependent on their ability to adapt to changing environments.

It was formerly believed that apomictic

1

taxa (eg S. arranensis

and

S. pseudofennica) were genetically

invariant and as a consequence held little evolutionary potential (Darlington 1939; Stebbins 1950). It was

thought that asexual organisms responded slowly to changing environments being unable to exchange and

compile favourable mutations that can lead to adaptive evolution. However, true obligate apomixis, in which

all possibility of sexuality has been lost, is a rare phenomenon and some sexuality continues to be a feature

of most apomictic plants (Nogler 1984; Asker and Jerling 1992). Clausen (1954) was among the first to

recognise that facultative apomixis does not necessarily lead to a loss of variation and evolutionary potential.

He argued that a combination of sexuality, which allows for the progressive production of new genotypes,

and apomixis, which permits the unlimited and faithful reproduction of the fittest genotypes, would enhance

rather than diminish a species capacity for adaptive change.

1 Apomixis: reproduction which has the superficial appearance of ordinary sexual cycle (amphimixis) but actually occurs

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2

OBJECTIVES

It is the aim of this report to review site files held by SNH, as well as published literature on the Arran

endemic whitebeams. This review will provide a definitive source on the status of these species.

The objectives are:

to review the evolutionary history of the Arran endemic whitebeams

to review and compile demographic and ecological data from published and unpublished sources

to discuss the genetic status of the Sorbus

complex on Arran

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3

DISTRIBUTION

3.1

Past distribution

Pollen studies on the vegetation history of north Arran show that several species of Sorbus, primarily

S. aucuparia

but also S. rupicola

or S. pseudofennica, have been components of the local woodland since

4,500 B.P. (Boyd & Dickson 1987). It is believed that at some stage in the post-glacial forest history of Arran

the

Sorbus

taxa had a much greater distribution throughout the then, more extensive forest (Boyd et al.

1988). Whilst the evidence indicates presence of the species at different sites from today’s populations,

there is no evidence for continual widespread distribution of the endemic hybrids. The present locations of

the Arran hybrids is likely to be a reflection of their former distribution. The hybrids may have been able to

exploit an ecological niche that was outside the range of their parent species, S. aucuparia, and establish

in steep sided gorges and rocky outcrops (the habitat of the now locally extinct parent S. rupicola).

3.2

Current distribution

Populations of both S. arranensis

and S. pseudofennica

are limited to the steep-sided gorges in the north of

the Isle of Arran, Scotland. Previous botanical surveys have identified 14 sites where these taxa have been

located (Fig. 1, Table 1). Total population sizes of S. arranensis

and

S. pseudofennica

are 407 and

436 respectively (Table 1). Added together with 13 unidentified Sorbus

whitebeams (Burlison 1986),

the overall total of endemic whitebeams is 856. These figures represent a compilation of the last known

population sizes recorded for each taxon at each site. Individual tree data and grid references at eight sites

(A, B, C, E, I, J, L, M, N) surveyed by Robertson (1997) are at Appendix 1. Fifteen Sorbus

hybrids were

recorded at site K in 1951 (Green 1951, Table 2). However, they have not been observed since. It was

initially thought that fire was responsible for the local extinction however; Burlison (1986) thought it more

likely that it was a landslide.

The sites range from 10–350m above sea level and vary in aspect, exposure and slope. The climate is wet,

mild and windy with a mean annual rainfall ranging from 1778mm near the coast to 2159mm inland

(Ordnance Survey 1967). The soils at all sites are humus iron podsols and soils of alluvial origin (Macaulay

Institute for Soil Research 1982). The current vegetation of this area is predominantly upland moorland,

largely dominated by Molinia caerulea

(L.) Moench and Calluna vulgaris

(L.) (NCC 1986). Birch (Betula

spp.)

and rowan (Sorbus aucuparia) dominate the fragmented semi-natural woodland, with sporadic occurrences

of holly (Ilex aquifolium

L.), aspen (Populus tremula

L.), juniper (

Juniperus

spp.) and willow (Salix

spp.).

The woodland is generally sparse and of low stature (less than 8m tall).

The Arran whitebeams are unique amongst the endemic British Sorbus

species as they do not occur on

base-rich or limestone soils (Bignal 1980). The apparent absence of base enbase-richment may be explained in part

by the occurrence of shear zones in the granite parent rock (within Gleann Diomhan, and possibly at other

sites). Associated with these shear zones is the release of epidote, a rather unstable mineral of calcium,

aluminium and iron silicate, which weathers rapidly to release its component elements. Epidote zones will

be far more calcareous than the surrounding granites and will undoubtedly give rise to soils with chemical

characteristics similar to those derived from limestone (Bignal 1980).

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Figure 1 Endemic Sorbus hybrids sites (A–N) in the nor th of Arran (See Table 1 for site details and population sizes for each taxon)

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Table 1 Locations and population sizes of endemic Sorbus trees at 14 sites on Arran (Number of unidentified Sorbus hybrids in brackets)

Site and Site code S. arranensis S. pseudofennica Most recent survey

Grid reference Population size Population size

Diomhan Burn A 209 275 Robertson 1997

NR 925467

Diomhan Tributary B 32 23 Robertson 1997

NR 930467

Allt nan Calman C 24 33 Robertson 1997

NR 918454

Abhainn Bheag D 0 40 Robertson 1997

NR 924489

Catacol Burn E 33 40 Robertson 1997

NR 917457

Catacol Tributary E 8 25 Burlison 1986

NR 917457 (11)

Creag na h-lolaire F 1 (2) Burlison 1986

924475

Allt nan Champ G 30 0 Burlison 1986

936430

Garbh Coire Dubh H 24 0 Burlison 1986

951432

Allt Easan Boirach I 11 0 Robertson 1997

NR 953474

Allt Easan Boirach J 3 0 Robertson 1997

NR 952467

Allt a’ chrithich K 0 0 Burlison 1986

NR 944477

Allt Dubh L 27 0 Robertson 1997

NR 944470

Allt Easan Boirach M 4 0 Robertson 1997

NR 945496

North Glen Sannox N 1 0 King 1981

NR 964457

Total 407 436

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4

MORPHOLOGY

S. arranensis

and

S. pseudofennica

are often described as small slender trees with maximum heights of

7.5m and 7m respectfully. However, this form tends to occur only in sheltered positions away from grazing

pressure and is rarely seen in natural populations (Burlison 1987). Trees of both taxa are often multi-stemmed

and less than 2m high.

The leaves of S. arranensis

are covered with an uneven grey-white felt. They are broadest below the middle

and are pinnately lobed to varying degrees, but rarely have any free leaflets (with the exception of those on

suckers, leading shoots and in the shade). The leaves on a single tree can vary in length/breadth ratio and

depth of lobing. Spur shoots are more constant in shape and degree of lobing and are therefore most

suitable for taxonomic comparisons (Rich 2003, pers. comm.). Flowers are 8–10mm in diameter with cream

petals. Fruits are 8–10mm, scarlet and are longer than they are broad.

The leaves of S. pseudofennica

differ from those of S. arranensis

in that they are broadest in the middle and

always pinnate at the base, with at least 1–4 pairs of free leaflets. They are also covered with an uneven

grey-white felt. Flowers are 10–12mm diameter with white petals. The fruits are identical to those of

S. arranensis. Both taxa flower late in May to early June and fruit from September to October.

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5

HYBRID ORIGINS

A combination of morphological analysis (Willmot 1934; Warburg 1952; Hull and Smart 1984),

cytological investigation (McAllister 1986; Liljefors 1953, 1955) and recent molecular marker studies

(Nelson-Jones

et al. 2002; Robertson et al. 2004a) have confirmed that both endemic Sorbus

taxa are

of hybrid origin. S. arranensis

(2n = 3x = 51) is a triploid hybrid (chromosome constitution AAB) formed

between the widespread diploid species S. aucuparia

(2n = 2x = 34) (BB) and the autotetraploid

S. rupicola

(2n = 4x = 68) (AAAA). Subsequent hybridisation of an unreduced gamete of S. arranensis

with

S. aucuparia

has given rise to the allotetraploid S. pseudofennica

(2n = 4x = 68) (AABB). Robertson et al.

(2004a) demonstrated at least three independent hybrid origins for S. arranensis

and five for S. pseudofennica.

There is also a suggestion that further diversity is being produced within the complex by crosses between

S. pseudofennica

and

S. aucuparia

(Robertson et al. 2004b). A small number of these established plants

have been found to display an unusual leaf morphology (Lusby 1996, pers. comm.). This is intermediate

between S. aucuparia

(all leaflets free) and S. pseudofennica

(all except two basal pairs of leaflets fused)

(Fig. 2). Their leaf morphology is closely matched to S. menichii senso lato, which is found only in

Scandinavia. This Scandinavian hybrid is thought to have been derived from a cross between S. aucuparia

and S. hybrida

(= S. pseudofennica).

Hull and Smart (1984) found that although there was a significant difference in leaf morphology between

S. arranensis

and

S. pseudofennica

there was still a 35% overlap of leaf characters between the two

hybrid taxa. It was suggested the overlap could reflect hybridisation events between S. arranensis

and

S. pseudofennica. However, as Hull and Smart measured phenotypically plastic leaf characters it is possible

that environmental variability could also account for their findings. Robertson (2000) found no molecular

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Figure 2 Leaf morphology of the novel Sorbus type shown to be intermediate between

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6

REPRODUCTION

6.1

Apomixis

The endemic Sorbus

species on Arran possess unusual breeding systems. Analysis of molecular marker

data in maternal and progeny genotype arrays (Robertson et al. 2004b) indicates that the Arran Sorbus

hybrids reproduce asexually. S. arranensis

produces seed exclusively by apomictic reproduction.

In S. pseudofennica

apomixis also takes place, but a proportion of its seeds are produced sexually, probably

by random outcrossing.

6.2

Flower and fruit production

Reproductive output is limited for both taxa. A complete survey of all known Sorbus

hybrid sites was

undertaken over six years. Laing started the survey in 1980, followed by a number of different recorders

and was finished by Burlison in 1986 (hereafter referred to as Laing et al. 1980/86). They reported that

only 16% of S. arranensis

and 17% of S. pseudofennica

trees produced any flowers or fruit. Doar (1989)

recorded 26% for S. arranensis

and 20% for S. pseudofennica

and Hull and Smart (1984) reported less

than 10% for both taxa. S. aucuparia

produces significantly more fruit and developed seeds than both

hybrids (Doar 1989; Vickery et al. 1998).

Doar (1989) reported that the reproductive potential of S. arranensis,

S. pseudofennica

and S. aucuparia

is determined by age, height and/or stem diameter. However, as Doar initially derived the ages of the trees

from their size, the study does not allow for the effects of size and age, on reproductive output, to be

separated. From survey data (Laing et al. 1980/86; Robertson 1997) it would appear that size, not the

age of a tree, is the critical factor in determining when a tree starts producing flowers. In both surveys there

was not a single tree under 1.5m high with flowers or fruits and records of tagged trees (Appendix 2) show

that many of these were at least 25 years old. Approximately 50% of all Sorbus

hybrids were less than 1.5m

tall in both surveys. Poor soils, climate, exposure and the presence of large and small herbivores are thought

to be the primary reasons for this lack of growth and subsequent loss of reproductive potential.

Seed dispersal is predominantly by frugivorous birds mainly migrating redwings and field fares. They have

a marked preference for S. aucuparia

berries but do feed from both S. arranensis

and S. pseudofennica

(Robertson 2000).

6.3

Vegetative reproduction

Epicormic regeneration and suckering have been observed in both S. arranensis

and

S. pseudofennica.

Epicormic shoots tend to regenerate from trunks or branches, whereas suckers are sprouts that form from the

roots of existing trees and tend to form new individuals in the process. Damage or disturbance to the tree

can stimulate both types of regeneration. Twenty three trees were seen to produce new shoots from what

appeared to be old and damaged stumps, or fallen trees, and lateral clonal spread of up to 2m, from root

suckering, was recorded for five trees (Appendix 1). Suckering has also been recorded in S. aucuparia

(Kullman 1986) and is common in S. torminalis (Lloyd 1977). The full extent of suckering by the Sorbus

hybrids is not known and may play a significant part in their reproduction.

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7

POPULATION DYNAMICS

7.1

Sur vey histor y

When population counts are compared there appears to be a trend of an increase in trees over time.

This apparent increase in population size may be attributed to variation in survey methods. Earlier studies

counted only established trees (eg Green 1951; Colville 1970) whereas later counts tended to include

seedlings (eg Kerr 1970; Laing et al. 1980/86; Robertson 1997). Green’s 1951 estimate of the number

of endemic whitebeams for Gleann Diomhan (200) was shown to be an underestimate by 43%, when a

more detailed survey (mapping the trees not estimating numbers) was carried out in 1961 by Huxely (286).

The subsequent rise in Glean Diomhan population numbers (406) reported by Kerr in 1970, is possibly the

result of seedlings being included in the count for the first time. Even among surveys that did record seedlings

fluctuations in numbers may simply reflect annual variations in seedling production, the majority of which

never grow into adults. Further more, observers visited different sites at different times making temporal

comparison of abundance difficult.

7.2

Population age structure

Confidence in this trend, of an increase in population size, diminishes further, as it is doubtful that natural

regeneration has been sufficient for the maintenance of S. arranensis

and

S. pseudofennica

populations

(Bignal 1980; Boyd et al. 1988). A contrasting picture is presented by Doar (1989), who concluded

that populations of S. arranensis

and

S. pseudofennica, within the NNR, were healthy and regenerating

normally. Frequency distributions were all characterised by a large number of young trees with frequency

decreasing steadily with increasing age. However, these results should be treated with caution. With Sorbus

it is difficult to get reliable estimates of population age structure as trees often coppice and produce several

new stems after old trunks die back. Counts of tree rings by coring, or indirect measures such as diameter

at breast height (DBH), can show the age of an individual trunk, but not necessarily the age of the tree as

the rootstock may be much older.

7.3

Natural regeneration

Natural regeneration of both taxa has occurred in sheltered positions (Bignal 1980). Although recruitment

of seedlings was observed, there has been no real evidence of any long term establishment. For example,

seedlings recorded in 1971 and listed for revisiting in 1972 had perished (NCC 1972). It is not possible

to judge the success of the 101 seedlings identified and tagged in 1980/86, as the progress of these

plants was not checked until Robertson in 1997. Unfortunately by this time the majority of tags, used to

identify adult trees and seedlings, had fallen off or disappeared. Only 81 trees had retained their tags from

a total of approximately 1000 (Appendix 2). One seedling, originally numbered 898 and <15cm tall

(Laing

et al. 1980/86) had been re-numbered in 1997 as 1267. Over this period it had only reached

0.3m high and was noted as moribund with only three little twigs left. The success of the 12 seedlings and

38 young trees noted by Robertson in 1997 (Appendix 3) will not be known until the next survey.

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Table 2a Sur vey histor y of Arran Sorbus hybrids in Glenn Catacol and Gleann Diomhan, sites A–F

Locality Site Recorder Arr* Ps** Un*** Total

code

Diomhan Burn A Green 1951 – – – c. 200

Huxley 1961 141 145 – 286

Kerr 1970 193 213 – 406

Laing et al. 80/86 293 302 78 673

Robertson 1997 212 274 – 486

Diomhan Burn B Laing 1980 – – – c. 40

Tributary Laing et al. 80/86 39 13 1 53

Robertson 1997 32 13 – 45

Allt nan Calman C Green 1951 – – – c. 30

Kerr 1971 14 38 – 52

Laing et al. 80/86 29 36 – 65

Robertson 1997 24 33 – 57

Abhainn Bheag D Green 1951 – – – c. 40

Kerr 1971 – 30 – 30

Laing 1979 17 18 – 35

Laing et al. 80/86 – 40 – 40

Robertson 1997 – 40 – 40

Catacol Burn E Green 1951 – – – c.20

Kerr 1971 11 72 – 83

King 1981 33 16 2 51

Laing et al. 80/86 38 53 2 93

Robertson 1997 33 43 – 76

Catacol Tributary E Laing et al. 80/86 8 25 11 44

Creag na h-lolaire F Bignal 1979 – – – 4

King 1981 – – 4 4

Laing et al. 80/86 1 – 2 3

* Arr = Sorbus arranensis

** Ps = Sorbus pseudofennica

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Table 2b Sur vey histor y of Arran Sorbus hybrids in Gleann Easan and Glen Iorsa, sites G–N

Locality Site Recorder Arr* Ps** Un*** Total

code

Allt nan Champ G Green 1951 – – – c. 15–20

King 1981 23 – – 23

Laing et al. 80/86 30 – – 30

Garbh Coire Dubh H King 1981 10 – – 10

Laing et al. 80/86 24 – – 24

Allt Easan I Green 1951 – – – c. 10

Biorach Colville 1970 – – – 4

Laing 1981 6 – – 6

Laing et al. 80/86 9 – – 9

Robertson 1997 11 – – 11

Allt Easan J Laing et al. 80/86 3 – – 3

Biorach Robertson 1997 3 – – 3

Allt a’ chrithich K Green 1951 – – – 15

Colville 1970 – – – 0

Laing 1980 – – – 0

King 1981 – – – 0

Burlison 1986 – – – 0

Robertson 1997 – – – 0

Allt Dubh L Green 1951 – – – 30

Colville 1970 19 – – 19

Laing et al. 80/86 32 – – 32

Robertson 1997 27 – – 27

Allt Easan M Laing et al. 80/86 3 – – 3

Biorach Robertson 1997 4 – – 4

North Glen N King 1981 – – 1 1

Sannox

* Arr = Sorbus arranensis

** Ps = Sorbus pseudofennica

(21)

7.4

Planted seedlings

Arran endemic whitebeams (seedlings and saplings) were planted at different sites within the NNR in 1964,

1977 and 1979/80. Their progress has been monitored more closely than naturally regenerated seedlings.

In the spring of 1964 40 endemic whitebeam seedlings were planted in peat, on which Sorbus

trees do

not often regenerate naturally. When they were visited the following August, at least one third of the trees

had been severely eaten by voles (Huxely 1965). As a trial, a few of these trees were protected with wire

netting. By 1969 some of the caged hybrids appeared to be surviving but others were unhealthy or dead

(Nelson 1969). The observation that the original trees were eaten by voles was questioned by Nelson

(1969) who found no evidence of tunnels in the vegetation normally associated with high vole populations.

Bignal (1978) examined many trees thought to have been vole damaged, and concluded the damage was

more likely to have been caused by hares.

The remaining caged seedlings from the 1964 planting had their cages removed and were tagged

(450–460) at an unspecified date. Their progress was monitored frequently by Bignal in the late 1970’s

(Bignal 1977, 1978, 1979) and during the 1980/86 survey (Laing et al. 1980/86) (Appendix 4).

Over this period the majority of trees had experienced annual die-back and regeneration; two had died.

The trees only reached heights up to 1m in 16 years. The fate of two trees with tags remaining (452 and

457) was recorded in 1997 (Appendix 4). One had reached 2m and was as an ageing bushy tree.

The other had regenerated having been recorded dead in 1977, 1979 and 1980. By 1997 it had

reached a height of 1m.

Trees can remain small and stunted throughout their lifetime. 55 trees from the 1970 survey (Kerr 1970)

were traceable to 1997 (Robertson 1997) (via the 1980/86 survey, Appendix 2). Twenty five of these trees

were less than 1m tall in 1970 and by 1997 only five had surpassed 1m (Table 3). A combination of

grazing (hares and deer) and fatal damage to buds (wind blast, birds and moth larvae (Argyresthia

sorbiella)) are thought to be responsible for their lack of stature.

Severe hare damage and die-back was observed on trees planted in 1977 (Appendix 4). Despite this, they

established better than trees planted in 1964. Two trees planted in 1980 had reached 2m by 1997 and

were healthy bushy trees (Appendix 4). The success of these trees, compared with seedlings planted in

1964, is thought to be attributed to the planting of larger saplings in a more sheltered, less waterlogged site.

These observations show that if seedlings can establish, they have a good chance of survival. However,

where they establish will be a dominant factor in determining their reproductive potential. Seedlings in

exposed, marginal sites are likely to remain small and stunted compared with those in sheltered sites which

are more likely to survive and reach heights that promote flowering and fruiting.

(22)

8

GENETIC DIVERSITY

Populations of obligate apomict taxa such as S. arranensis

are made up entirely of clonal lineages.

Clonal variation, or genetic diversity, depends on the number of primary hybridisation events between

genetically distinct individuals of each progenitor species, with each new hybridisation event producing

a new clone. Subsequent mutations that are introduced into the clonal lineage produce additional variation.

For populations of facultative agamospermous taxa such as S. pseudofennica

there is the potential for

greater genetic diversity. Clonal diversity will depend on not only the number of primary hybridisation events

and mutations, but any degree of sexual reproduction within the taxa will lead to genetic recombination and

the production of new genotypes.

Clonal diversity has been reported within both S. arranensis

and S. pseudofennica

(Robertson et al. 2004a).

Three

S. arranensis

clones were detected from a sample of 179 individuals, distributed among eight

populations; and eight S. pseudofennica

clones were detected from a sample of 140 S. pseudofennica

individuals, distributed among five populations (Table 4). As site A (the NNR) holds 51% and 63% of the

total population sizes of S. arranensis

and S. pseudofennica

respectively, it may have been reasonable to

expected that the NNR would contain a representative sample of the total genetic diversity for each species.

However, this is not the case, site A has only a single S. arranensis

clone present (A1). S. arranensis

clone

A2 was found in sites B, E and J; and clone A3 was limited to site J. As with S. arranensis

not all

S. pseudofennica

clones were found in Site A; P4 was found in site B, P6 in site C and P7 in site B (Table 4).

Table 3 Height and fate of trees in 1970, 1980/86 and 1997

Ps = S. pseudofennica Arr = S. arranensis

1997 Grid Species Height (m) Fate 1980–86 Height Fate 1970 Height

Identifier reference 1997 1997 Identifier 1980–86 1980–86 Identifier* 1970

1377 92674663 Ps 0.75 Slim tree 942 0.7 – 354 0.03 1135 92654668 Ps 1 – 708 1 – 252 0.15 1265 92764656 Ps 0.75 – 993 0.22 Prostrate 47 0.15 1128 92554670 Arr 1 – 457 0.6 40% dead 286 0.3 wood D35 92564670 Ps 0.75 Browsed 168 0.4 Browsed 205 0.3 1208 92594673 Arr 1 Moribund 736 0.7 – 380 0.3 1419 92644664 Ps 1 Moribund 9 0.5 – 357 0.3 1139 92654668 Ps 0.5 – 707 0.9 – 250 0.3 1353 92664661 Ps 1 – 935 0.54 – 90 0.3 1375 92674664 Ps 0.15 Moribund 957 0.26 – 101 0.3 1165 92704666 Ps 0.3 Slim tree 696 0.5 – 368 0.3 1271 92774658 Ps 0.1 Moribund 984 0.44 – 332 0.3 1340 92854651 Arr 0.15 Moribund 843 0.3 40% dead 322 0.3

wood

1098 92564671 Arr 0.5 Browsed 165 0.4 – 209 0.5 1161 92704666 Ps 0.2 Moribund 692 1.4 – 366 0.6 1313 92724660 Ps 1.5 – 990 1 – 347 0.6

(23)

Table 3 (continued)

1997 Grid Species Height (m) Fate 1980–86 Height Fate 1970 Height

Identifier reference 1997 1997 Identifier 1980–86 1980–86 Identifier* 1970

1240 92744665 Arr 2 Bushy tree 681 1 – 112 0.6 1204 92574673 Arr 2 Bushy tree 739 1.17 – 230 0.66 1409 92654664 Ps 1 – 961 0.9 35% dead 117 0.66

wood

1401 92654665 Ps 2.5 – 965 3.5 Flowering 112 0.66 1133 92654668 Ps 2 – 709 1.5 – 362 0.66 1281 92774658 Ps 1.5 Slim tree 894 1.4 30% dead 52 0.66

wood

1283 92774658 Ps 0.75 Slim tree 985 0.5 – 50 0.66 1325 92704659 Ps 1 – 905 1.16 – 75 0.7

* Trees were given a new number and tag in 1980/86. The old tags, fixed in 1970, were removed.

These results on clonal diversity can be compared with a previous morphometric study of S. arranensis

and

S. pseudofennica

by Hull and Smart (1984). They found considerable variation in hybrid index (based on

leaf characters measured in the field, which are subject to considerable environmentally induced variation)

for both S. arranensis

and

S. pseudofennica. However the variation was continuous and they were

consequently unable to distinguish individual clones.

Table 4 Number of individuals of multilocus genotypes in S. arranensis and S. pseudofennica at nine sites (A–M) on Arran

Site code S. arranensis S. pseudofennicagenotypes

genotypes A1 A2 A3 P1 P2 P3 P4 P5 P6 P7 P8 A 90 0 0 21 52 1 0 4 0 0 1 B 11 5 0 2 0 0 4 0 0 1 0 C 14 0 0 16 0 6 0 0 1 0 0 D 0 0 0 14 0 0 0 0 0 0 0 E 20 1 0 19 0 0 0 0 0 0 0 I 8 0 0 0 0 0 0 0 0 0 0 J 1 1 1 0 0 0 0 0 0 0 0 L 23 0 0 0 0 0 0 0 0 0 0 M 4 0 0 0 0 0 0 0 0 0 0

(24)

9

EVOLUTIONARY POTENTIAL

Molecular marker analysis (Robertson et al. 2004a, 2004b) has demonstrated that the Sorbus

complex on

Arran is an actively evolving entity that does not rely solely on rare hybridisation events and mutation for the

generation of new genotypic diversity. Although the triploid taxon S. arranensis

is an obligate apomict with

relatively little variability, it has given rise on multiple occasions to a tetraploid taxon, S. pseudofennica,

which produces a substantial proportion of its seed through sexual production. These sexually produced

seeds have the ability to establish in natural populations, significantly increasing the diversity of genotypes

present on Arran. There is also a suggestion that further diversity is being produced within the complex by

crosses between S. pseudofennica

and S. aucuparia.

From an evolutionary perspective S. aucuparia, S. pseudofennica

and S. arranensis

have an integrated and

dynamic role in creating new Sorbus

genotypes. From a conservation perspective, it is important to maintain

(25)

10

DISCUSSION

The threatened endemic hybrid whitebeams, S. arranensis

and S. pseudofennica, are limited to 13 sites on

Arran and support a relatively small number of individuals (856). Such small populations are susceptible to

demographic fluctuations which increase the probability of local extinction by chance (Richter-Dyn and

Goel 1972). McVean (1954) considered Arran’s endemic whitebeams, to be closer to extinction than any

other tree or shrub in Scotland (with the exception of Salix lanata). An uneven age distribution and scattered

occurrence of both S. arranensis

and

S. pseudofennica

were the basis for these concerns and used as

justifications for the establishment of the Gleann Diomhan NNR. The reserve was established in 1956 with

the aim of ensuring the long term survival of S. arranensis

and S. pseudofennica. Bignal (1980) repeated

concerns of an uneven age structure; he noted that large trees had been dying and regeneration was failing

to provide adequate replacements. These observations by Bignal and McVean have led to a number of

demographic and ecological studies in an attempt to identify the critical factors that are limiting population

size and distribution. However there is still a shortage of quantitative evidence, on the dynamics of the

Sorbus

populations, to support McVean and Bignal’s observations.

The studies incorporated in this report present a complex and often contradictory picture of population

dynamics. Observed trends of increasing numbers of trees over time conflict with a reported lack of

recruitment. The increase in population numbers appears to be a result of inconsistencies in survey method.

The lack of recruitment, and high mortality rates, observed by other studies gives cause for concern

regarding the regeneration potential of these Sorbus

populations. It is only once further monitoring of sites

has been undertaken (using a consistent methodology) and repeated over time, that a true picture of

population trends will become evident.

Detailed observations within the studies have revealed significant findings that may in part explain the

observed lack of regeneration of both taxa. It would appear that size is a limiting factor in determining when

a tree starts reproducing. Laing et al. (1980/86) and Robertson (1997) did not record or observe a single

tree under 1.5m high that had produced flowers or fruits. In both surveys it was found that approximately

50% of the total Sorbus

hybrid population were less than 1.5m high. This figure does not represent a healthy

regenerating population as records show that many of these trees were at least 25 years old and are unlikely

to have ever reproduced. Observations of trees planted in the NNR show that poor soils, climate, exposure

and the presence of large and small herbivores are the primary causes for this lack of stature and subsequent

loss of reproductive potential.

10.1 Recommendations for site management

The endemic hybrids grow on rocky crags and steep sided slopes which make detailed surveys an extremely

challenging endeavour. It is important to identify a population and/or a permanent sample plot within the

NNR that is not only a representative cohort of trees but is relatively accessible and safe to survey. This would

enable data to be collected reliably, within shorter time intervals and in a systematic manner that will reduce

error that may result from changes in recording personnel. Site E, Catacol Burn (NR 917457) is an ideal

population to study; there are approximately equal numbers of S. arranensis

and

S. pseudofennica

trees,

seedlings have been observed for both taxa and it is easily accessible. Further inspection of the NNR will

be needed to identify a suitable permanent sample plot within its boundary.

(26)

To increase the chance of seedling establishment and survival to reproductive capacity, it would be

beneficial if additional scrub woodland was planted, or encouraged to develop naturally, at the sites where

the

Sorbus

hybrids are found. The buffer zone that would be provided by the new surrounding woodland

would primarily provide shelter, but also increase soil enrichment, slow soil erosion and dampen the effects

of large and small herbivores (by providing additional fodder). It is possible that by being part of a larger

woodland, as was the case historically, these stunted trees will be released from their annual growth and

die-back cycle and start reproducing more successfully.

The re-creation of more sheltered conditions, through the establishment of scrub woodland in the reserve,

has been an objective since the creation of the NNR. It would be beneficial however, if this policy was

extended to all sites where Sorbus

trees are found. Robertson et al. (2004a, 2004b) have shown that the

Sorbus

complex on Arran is an actively evolving entity with new genotypes being generated throughout the

range of the endemic taxa. Sites A, B, C and E are priorities for conservation as these sites contain the

majority of known Sorbus

hybrid genotypes.

To maximise the potential for evolution of this complex and the long term survival of an endemic Sorbus

entity

on Arran, the conservation management objective should be to ensure that all the components of the

evolutionary complex, S. arranensis, S. pseudofennica

and S. aucuparia

are retained in the northern glens

of Arran. The aim must be to perpetuate the dynamic evolutionary processes that have given rise to the

endemic taxa in situ, rather than statically to preserve the named taxonomic entities that have emerged from

this process.

(27)

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APPENDIX 1 – 1997 population sur

vey data.

Previous ID will be 180/86 unless * = 1970 identification tag

1997 Grid Species Location Site Height P revious ID Comments identifier reference NR code m DII 92274701 S. arranensis Gleann Diomhan A 2

Many young shoots coming out of old trunk. Deeply lobed leaves

D13 92284699 S. pseudofennica Gleann Diomhan A 3

Fallen trunk with many young shoots coming up

D15 92294699 S. pseudofennica Gleann Diomhan A 2.5 Skinny tree D20 92314697 S. arranensis Gleann Diomhan A 1002 92334698 S. arranensis Gleann Diomhan A 1

Moribund. Only two small branches growing down into stream. Only just attached to bank. Deeply lobed leaves

1004 92344696 S. arranensis Gleann Diomhan A 2 1001 92354694 S. pseudofennica Gleann Diomhan A 1.5 Skinny tree D38 92354697 S. arranensis Gleann Diomhan A 0.75

Browsed. Deeply lobed leaves

D17 92374692 S. pseudofennica Gleann Diomhan A 4

Large old sprawling tree

1003 92374692 S. pseudofennica Gleann Diomhan A 2

Similar leaf for

m to

S.arranensis

with deeply lobed

leaves 1005 92374692 S. pseudofennica Gleann Diomhan A 2 D42 92384689 S. arranensis Gleann Diomhan A 1

Old bushy tree

1011 92384689 S. pseudofennica Gleann Diomhan A 2 1009 92384690 S. pseudofennica Gleann Diomhan A 2 1007 92384691 S. pseudofennica Gleann Diomhan A 2 D40 92394690 S. arranensis Gleann Diomhan A 3.5

Large sprawling old tree. Deeply lobed leaves

D19 92394690 S. pseudofennica Gleann Diomhan A 1 Bushy tree D21 92394690 S. pseudofennica Gleann Diomhan A 3 Slim tree 62 D5 92394690 S. pseudofennica Gleann Diomhan A 4

Bushy old tree

4 8 1012 92404691 S. arranensis Gleann Diomhan A 3 1013 92404691 S. pseudofennica Gleann Diomhan A 3

(31)

Appendix 1 (continued) 1997 Grid Species Location Site Height P revious ID Comments identifier reference NR code m 1014 92444683 S. arranensis Gleann Diomhan A 1

New growth from old tree

D25 92444683 S. pseudofennica Gleann Diomhan A 2 D48 92454680 S. arranensis Gleann Diomhan A 1 Bushy tree 1020 92454680 S. arranensis Gleann Diomhan A 1 Young tree 1020a 92454680 S. arranensis Gleann Diomhan A 0.75 1022 92454680 S. arranensis Gleann Diomhan A 1 D27 92454680 S. pseudofennica Gleann Diomhan A 1 Old tree D46 92454681 S. arranensis Gleann Diomhan A 1 Old tree 1015 92454686 S. pseudofennica Gleann Diomhan A 0.3 Young sapling D44 92464684 S. arranensis Gleann Diomhan A

Land slide caused old tree to fall. However

, new

shoots coming out of fallen brances. Deeply lobed leaves

1017 92464685 S. pseudofennica Gleann Diomhan A 1.5

Bushy tree. Similar leaf for

m to

S.arranensis

with

deeply lobed leaves

D50 92474675 S. arranensis Gleann Diomhan A 2 Old tree 1026 92474675 S. arranensis Gleann Diomhan A 2.5 Old tree 1028 92474676 S. arranensis Gleann Diomhan A 1 Old tree 1030 92474676 S. arranensis Gleann Diomhan A 0.75

Old tree. Deeply lobed leaves

1032 92474676 S. arranensis Gleann Diomhan A 1

Old tree. Deeply lobed leaves

1034 92474676 S. arranensis Gleann Diomhan A 2

Old tree. Deeply lobed leaves

1038 92474677 S. arranensis Gleann Diomhan A 1

Old tree. Deeply lobed leaves

1040 92474677 S. arranensis Gleann Diomhan A 3

Old tree. Deeply lobed leaves

1042 92474678 S. arranensis Gleann Diomhan A 3

Old tree. Deeply lobed leaves

D4 92474682 S. arranensis Gleann Diomhan A 2

Growing horizontally into gorge

1016 92474683 S. arranensis Gleann Diomhan A 4

(32)

Appendix 1 (continued) 1997 Grid Species Location Site Height P revious ID Comments identifier reference NR code m D23 92474683 S. pseudofennica Gleann Diomhan A 2 1036 92484676 S. arranensis Gleann Diomhan A 1.5 D2 92484678 S. pseudofennica Gleann Diomhan A 3 Small 1m of fshoot nearby D2A 92484679 S. arranensis Gleann Diomhan A 1 Looks like an of

f shoot of D2 but is not

1046 92484681 S. arranensis Gleann Diomhan A 2 1023 92484681 S. pseudofennica Gleann Diomhan A 2.5 Scruf fy old tree 1018 92484682 S. arranensis Gleann Diomhan A 1.5 1044 92484682 S. arranensis Gleann Diomhan A 2 1019 92484682 S. pseudofennica Gleann Diomhan A 1 1024A 92494671 S. arranensis Gleann Diomhan A 1056 92494674 S. arranensis Gleann Diomhan A 3

Bushy old tree

1058 92494674 S. arranensis Gleann Diomhan A 2

Old skinny tree

1062 92494674 S. arranensis Gleann Diomhan A 1 Young tree 1060 92494674 S. arranensis Gleann Diomhan A 1 Young tree 1052 92494674 S. arranensis Gleann Diomhan A 3

Large old tree

D29 92494674 S. pseudofennica Gleann Diomhan A 1 1054 92494675 S. arranensis Gleann Diomhan A 1054A 92494675 S. arranensis Gleann Diomhan A 2 1048 92494679 S. arranensis Gleann Diomhan A 3

Bushy old tree

1024 92504671 S. arranensis Gleann Diomhan A 2 1064 92514670 S. arranensis Gleann Diomhan A 2.5

Large bushy old tree

1066 92514670 S. arranensis Gleann Diomhan A 1 1068 92514671 S. arranensis Gleann Diomhan A 4

Large bushy old tree

1025 92514676 S. pseudofennica Gleann Diomhan A 3

(33)

Appendix 1 (continued) 1997 Grid Species Location Site Height P revious ID Comments identifier reference NR code m 1130 92524677 S. arranensis Gleann Diomhan A 2 1132 92524677 S. arranensis Gleann Diomhan A 3 Bushy tree D1 92534671 S. pseudofennica Gleann Diomhan A 4

Large bushy tree

1070 92534674 S. arranensis Gleann Diomhan A 2

Old Skinny tree. Not an individual tree it is connected to D 52

1050 92534674 S. arranensis Gleann Diomhan A 3

Growing horizontally into gorge. Not an individual tree it is connected to D 52

1136 92534676 S. arranensis Gleann Diomhan A 2 Bushy tree 1134 92534677 S. arranensis Gleann Diomhan A 2 Bushy tree 1090 92544667 S. arranensis Gleann Diomhan A 2.5 Bushy tree 1092 92544667 S. arranensis Gleann Diomhan A 1 1094 92544667 S. arranensis Gleann Diomhan A 1 Young tree 1027 92544669 S. pseudofennica Gleann Diomhan A 1

Moribund only two small branches

1029 92544669 S. pseudofennica Gleann Diomhan A 2 Bushy tree D52 92544673 S. arranensis Gleann Diomhan A 3 768 (387*)

Two young shoots growing out of old tree

D3 92544673 S. pseudofennica Gleann Diomhan A 3 771 Slim tree D31 92544673 S. pseudofennica Gleann Diomhan A 3 Slim tree 1138 92544676 S. arranensis Gleann Diomhan A 1.5

Growing horizontally from bank

1140 92544676 S. arranensis Gleann Diomhan A Slim tree 1072 92554668 S. arranensis Gleann Diomhan A 3

Moribund old tree

1074 92554668 S. arranensis Gleann Diomhan A 2.5 1078 92554668 S. arranensis Gleann Diomhan A 0.75

Little old tree with deeply lobed leaves

1080 92554668 S. arranensis Gleann Diomhan A 0.75 Ve ry

young tree with deeply lobed leaves

1082 92554668 S. arranensis Gleann Diomhan A 0.75 Ve ry young tree 1084 92554668 S. arranensis Gleann Diomhan A 0.75 Ve ry young tree

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Appendix 1 (continued) 1997 Grid Species Location Site Height P revious ID Comments identifier reference NR code m 1086 92554668 S. arranensis Gleann Diomhan A 0.75 Ve ry young tree 1088 92554668 S. arranensis Gleann Diomhan A 0.75 Ve ry young tree 1096 92554668 S. arranensis Gleann Diomhan A 1

Skinny young tree

D33 92554668 S. pseudofennica Gleann Diomhan A 2

Old tree with two new shoots

1128 92554670 S. arranensis Gleann Diomhan A 1 457

Skinny tree with silver tag

1142 92554671 S. arranensis Gleann Diomhan A 2 Par t old par t new tree 1144 92554671 S. arranensis Gleann Diomhan A 1146 92554671 S. arranensis Gleann Diomhan A 1.5 Skinny tree 1148 92554671 S. arranensis Gleann Diomhan A 3 Bushy tree 1089 92554671 S. pseudofennica Gleann Diomhan A 4 Old tree 1091 92554671 S. pseudofennica Gleann Diomhan A 1160 92554673 S. arranensis Gleann Diomhan A 2 Skinny tree 1162 92554673 S. arranensis Gleann Diomhan A 4 1076 92564668 S. arranensis Gleann Diomhan A 1 Bushy tree 1116 92564668 S. arranensis Gleann Diomhan A 2 1031 92564668 S. pseudofennica Gleann Diomhan A 0.75 Ve ry young tree 1085 92564668 S. pseudofennica Gleann Diomhan A 2 1087 92564668 S. pseudofennica Gleann Diomhan A 0.3 Ve ry young tree 1118 92564669 S. arranensis Gleann Diomhan A 1.5 161 1120 92564669 S. arranensis Gleann Diomhan A 1.5 87 Old tree 1122 92564669 S. arranensis Gleann Diomhan A 1 1124 92564669 S. arranensis Gleann Diomhan A 0.75 Old tree 1126 92564669 S. arranensis Gleann Diomhan A 4 Old tree 1150 92564670 S. arranensis Gleann Diomhan A 3.5 Bushy tree

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Appendix 1 (continued) 1997 Grid Species Location Site Height P revious ID Comments identifier reference NR code m 1152 92564670 S. arranensis Gleann Diomhan A 1 Skinny tree 1154 92564670 S. arranensis Gleann Diomhan A 0.74 1156 92564670 S. arranensis Gleann Diomhan A 0.15 Browsed 1158 92564670 S. arranensis Gleann Diomhan A 0.3 77 Moribund 1101 92564670 S. pseudofennica Gleann Diomhan A 0.5 D35 92564670 S. pseudofennica

Gleann Diomhan, fenced area

A 0.75 168 Browsed D37 92564670 S. pseudofennica

Gleann Diomhan, fenced area

A 0.75 Young tree 1174 92564671 S. arranensis Gleann Diomhan A 1.5 1098 92564671 S. arranensis

Gleann Diomhan, fenced area

A

0.5

165

Old browsed tree

D58

92564671

S. arranensis

Gleann Diomhan, fenced area

A

1

Bushy old tree

D56

92564671

S. arranensis

Gleann Diomhan, fenced area

A

2

Bushy old tree

D54

92564671

S. arranensis

Gleann Diomhan, fenced area

A

1

Bushy old tree

D43

92564671

S. pseudofennica

Gleann Diomhan, fenced area

A

2

Skinny old tree

D41

92564671

S. pseudofennica

Gleann Diomhan, fenced area

A 1.5 1168 92564672 S. arranensis Gleann Diomhan A 2 1100 92564672 S. arranensis

Gleann Diomhan, fenced area

A 0.1 Seedling 1102 92564672 S. arranensis

Gleann Diomhan, fenced area

A 2 Old tree 1033 92564672 S. pseudofennica

Gleann Diomhan, fenced area

A 0.75 Browsed 1182 92564674 S. arranensis Gleann Diomhan A 4 Bushy tree 1184 92564674 S. arranensis Gleann Diomhan A 3

Deeply lobed leaves

1186 92564674 S. arranensis Gleann Diomhan A 3

Deeply lobed leaves

1188 92564674 S. arranensis Gleann Diomhan A 1.5 1190 92564674 S. arranensis Gleann Diomhan A 3 1192 92564674 S. arranensis Gleann Diomhan A 1

Figure

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