ORIGINAL ARTICLE

Reduced genetic diversity and sperm motility in the endangeredGran Canaria Blue Chaffinch Fringilla teydea polatzeki

Eduardo Garcia-del-Rey • Gunnhild Marthinsen • Pascual Calabuig •

Loly Estevez • Lars Erik Johannessen • Arild Johnsen •

Terje Laskemoen • Jan T. Lifjeld

Received: 17 October 2012 / Revised: 14 January 2013 / Accepted: 22 February 2013

� Dt. Ornithologen-Gesellschaft e.V. 2013

Abstract The Blue Chaffinch (Fringilla teydea) is

endemic to the Canary Islands and restricted to the pine

forests on Tenerife (ssp. teydea) and Gran Canaria (ssp.

polatzeki). While the teydea population is large and stable,

the polatzeki population underwent a dramatic decline in

the twentieth century and currently numbers less than 200

individuals. Here, we show that microsatellite allelic

diversity is lower in polatzeki than in teydea, consistent

with a genetic bottleneck scenario. Our genotyped polat-

zeki individuals, which were wild-caught but currently used

in a captive breeding programme, have the same allelic

diversity as free-ranging birds. However, the captive

polatzeki males seem to have reduced sperm motility as

compared with captive teydea males, which could be an

effect of reduced genetic diversity. Because polatzeki and

teydea are phylogenetically distinct, they should be rec-

ognized as Evolutionarily Significant Units by conservation

authorities. We also recommend maintaining the captive

polatzeki population as a pre-emptive measure against

extinction in the wild.

Keywords Allelic richness � Canary Islands � Extinction �Microsatellites � Sperm swimming speed

Zusammenfassung

Eingeschrankte genetische Vielfalt und Spermien-

beweglichkeit beim vom Aussterben bedrohten Teide-

Blaufinken (Fringilla teydea polatzeki) auf Gran

Canaria

Der Teide-Blaufink (Fringilla teydea polatzeki) ist auf den

Kanarischen Inseln endemisch und lebt ausschließlich in

den Pinienwaldern auf Teneriffa (ssp. teydea) und Gran

Canaria (ssp. polatzeki). Wahrend die Population auf

Teneriffa groß und stabil ist, erfuhr die Population auf Gran

Canaria im 20. Jahrhundert einen dramatischen Ruckgang

und umfasst zur Zeit weniger als 200 Individuen. In dieser

Arbeit zeigen wir, dass die allelische Vielfalt der Mikro-

satelliten bei Polatzeki geringer als bei Teydea ist, was im

Einklang mit einem genetischen ,,Engpass-Szenario‘‘steht.

Unsere genotypisch eindeutig identifizierten Polatzeki-In-

dividuen, die Wildfange waren und jetzt in Gefangenschaft

in einem Brutprogramm eingesetzt werden, zeigten die

gleiche allelische Vielfalt wie die Tiere im Freiland.

Aber die gefangenen Polatzeki-Mannchen scheinen ge-

genuber den Teydea-Mannchen eine reduzierte Sper-

mienbeweglichkeit zu haben, was an einer geringeren

genetischen Vielfalt liegen konnte. Weil Polatzeki und

Teydea phylogenetisch unterschiedlich sind, sollten sie

vom Naturschutz offiziell als Evolutionary Significant

Units (ESU) anerkannt werden. Wir empfehlen außerdem,

die derzeit in Gefangenschaft gehaltene Polatzeki-Popula-

tion weiterzufuhren als Vorsichtsmaßnahme gegen die

mogliche Ausrottung im Freiland.

E. Garcia-del-Rey

Macaronesian Institute of Field Ornithology,

C/Enrique Wolfson 11-3, 38004 Santa Cruz de Tenerife,

Canary Islands, Spain

G. Marthinsen � L. E. Johannessen � A. Johnsen �T. Laskemoen � J. T. Lifjeld (&)

Natural History Museum, University of Oslo, Blindern,

P.O. Box 1172, 0318 Oslo, Norway

e-mail: j.t.lifjeld@nhm.uio.no

P. Calabuig � L. Estevez

Wildlife Recovery Center ‘‘Tafira’’, Vivero Forestal,

Cabildo de Gran Canaria, 35017 Las Palmas de Gran Canaria,

Canary Islands, Spain

123

J Ornithol

DOI 10.1007/s10336-013-0940-9

Introduction

Taxonomic uncertainty represents a major challenge to

conservation biology (Frankham 2010), because evolu-

tionarily distinct lineages below the species level may

easily be overlooked in conservation efforts based on lists

of threatened species, like the IUCN Red List (IUCN

2012). Therefore, the concept of Evolutionarily Significant

Units (ESUs; Ryder 1986; Moritz 1994) has been launched

to define groups within a species that are phylogenetically

distinct. They are supposed to harbour an evolutionary

heritage of local adaptation and potential for evolutionary

change that makes them worthy of independent manage-

ment. Defining ESUs is particularly relevant for popula-

tions on oceanic islands, because such populations are

often small and spatially restricted, as well as phyloge-

netically distinct due to a long history of allopatric evo-

lution. This pattern is well documented for birds. Recent

avian classifications list about 10,000 species, with more

than 20,000 named subspecies (e.g. Gill and Donsker

2012). Although a majority of these subspecies may not

represent independent evolutionary lineages (Zink 2004), a

global survey found that a higher proportion of island-

dwelling than of continental subspecies were monophyletic

(i.e. 57 vs. 29 %; Phillimore and Owens 2006). It is also

well documented that island-dwelling birds have suffered a

high extinction rate in historic time (Johnson and Statt-

ersfield 1990) and are common on the global list of

threatened species (BirdLife International 2000). All of this

implies that island populations, and especially endemic

subspecies, require special attention when identifying

ESUs with a high risk of extinction.

The Blue Chaffinch (Fringilla teydea) is endemic to the

Canary Islands and restricted to the Canary pine forests

(Pinus canariensis) on the islands of Tenerife and Gran

Canaria (del Hoyo et al. 2010). Based on morphological

differences, the two populations are taxonomically descri-

bed as separate subspecies; ssp. teydea on Tenerife and ssp.

polatzeki on Gran Canaria (Bannerman 1922; del Hoyo

et al. 2010; Gill and Donsker 2012). The teydea population

was first discovered in the mid-nineteenth century whereas

the polatzeki population was found in the early twentieth

century (Bannerman 1963). Both taxa showed healthy

population sizes around 1910, but since then the polatzeki

population has declined severely, due to human-induced

habitat loss with extensive destruction and fragmentation

of the pine forest (Bannerman 1963). The close ecological

association between the Blue Chaffinch and its pine forest

habitat has been subject to several recent studies in teydea

(e.g. Garcia-del-Rey et al. 2009, 2010, 2011), whereas little

is known about specific habitat requirements and general

ecology of the polatzeki population (see Rodrıguez and

Moreno 2008). The Blue Chaffinch is classified as ‘‘Near-

Threatened’’ by IUCN (BirdLife International 2012),

because the total population size is estimated to

1,800–4,500 individuals, and the area of suitable habitat is

increasing on Tenerife. It may be down-listed to ‘‘Least

Concern’’ if the positive trend continues and plausible

actions are taken to reduce the threat of wildfires (BirdLife

International 2012). However, the polatzeki population on

Gran Canaria has been considered critically endangered by

the Canary Islands Government (Vice-council of the

Environment) since 1990 (Real Decreto 439/1990, 30

March), due to a small population size of about 250 indi-

viduals (Rodrıguez and Moreno 2004). Severe wildfires in

2007 seem to have reduced the remnant population even

further, down to an estimated 122 individuals (Carrascal

and Seoane 2008). Hence, there is no doubt that the

polatzeki population is seriously threatened by extinction,

but its official status as an endangered taxon is obscure.

Sequencing of mtDNA has revealed that the two sub-

species are reciprocally monophyletic (Pestano et al. 2000).

They therefore seem to qualify as two ESUs (sensu Moritz

1994), although it is not yet known whether they are also

significantly divergent at nuclear DNA markers. Surpris-

ingly, Pestano et al. (2000) found that the small polatzeki

population had higher mitochondrial genetic diversity than

teydea. A recent microsatellite study, comparing allelic

diversity in polatzeki before and after the severe forest fires

in 2007, also concluded that the population showed no

signs of a recent genetic bottleneck and had relatively high

levels of allelic diversity for microsatellite loci in endan-

gered birds (Suarez et al. 2012). It therefore seems as if the

polatzeki population has retained high levels of genetic

diversity despite a severe demographic bottleneck.

Here, we report a comparison of microsatellite allele

frequencies between the teydea and polatzeki populations,

using eight polymorphic loci analysed by Suarez et al.

(2012). From the contrast in census population size, we

would expect allelic diversity to be lower in polatzeki than

in teydea. Furthermore, with the evidence from mtDNA of

a long-term evolutionary divergence between populations

(Pestano et al. 2000), we would also expect differences in

allele size distributions. Our genotyped polatzeki individ-

uals were wild-caught individuals that are currently used in

a captive breeding programme run since 2005 by the local

authorities (Cabildo) in Tafira, Gran Canaria. We also

compared sperm motility in captive polatzeki males with

that of captive teydea males from Tenerife held in the same

facility, as there is some evidence that reduced genetic

diversity may impair sperm quality (Fitzpatrick and Evans

2009).

J Ornithol

123

Methods

We genotyped 16 polatzeki individuals used in the captive

breeding programme and 27 teydea individuals. All these

birds were wild-caught and presumably unrelated. In

addition, we genotyped 19 polatzeki offspring produced in

captivity for a separate analysis of potential inbreeding

among the captive birds. Blood samples were preserved in

absolute ethanol. Genomic DNA was extracted using a

commercial spin column kit (E.Z.N.A. DNA Kit; Omega

Bio-Tek) or a GeneMole� automated nucleic acid extrac-

tion instrument (Mole Genetics), following the manufac-

turers’ protocols. The PCR reaction volumes were 10 lL,

containing 0.6 mM dNTPs, 0.3 U Dynazyme II DNA

Polymerase (Finnzymes), 19 buffer solution (10 mM Tris–

HCl, 1.5 mM MgCl2, 50 mM KD and 0.1 % Triton X-100;

Finnzymes), 0.5 mM primer and 1 or 2 lL DNA extract

(approximately 50 ng template DNA). Primer sequences

for the eight microsatellites are given in Suarez et al.

(2009), and forward primers were fluorescently labelled

with HEX, NED or FAM (Applied Biosystems). Geno-

typing at a ninth marker (Ftey26; Suarez et al. 2009) was

attempted, but it failed to amplify in more than 50 % of the

individuals, and was therefore omitted from further anal-

yses. The PCR reactions were carried out separately for

each marker under the following conditions: 10 min at

94 �C, 35 cycles of 30 s at 94 �C, 30 s at either 50, 55 or

60 �C, and 30 s at 72 �C, and a final extension period of

10 min at 72 �C. Annealing temperatures were 50 �C for

Ftey8 and Ftey19, 55 �C for Ftey22, Ftey25, Ftey28,

Ftey29 and Ftey30, and 60 �C for Ftey20. The PCR

products were run on an ABI Prism 3130xl Genetic Ana-

lyzer (Applied Biosystems), multiplexing Ftey08, Ftey19,

Ftey20 and Ftey30 in one panel, and the remaining markers

in another. The results were scored in GeneMapper 4.0

(Applied Biosystems).

Allele frequencies, expected and observed heterozy-

gosities, and null allele frequency estimates were calcu-

lated in CERVUS 3.0.3 (Kalinowski et al. 2007),

deviations from Hardy–Weinberg equilibrium, the

inbreeding coefficient FIS and an estimate of genetic

structure (FST) between groups were calculated in Arlequin

3.5 (Excoffier and Schneider 2005). As the number of

unique alleles is expected to increase asymptotically with

the number of individuals genotyped, a comparison of

allelic diversity must control for differences in sample size.

This is the rationale behind the calculation of allelic rich-

ness (Leberg 2002), which is a permutation estimate of the

number of alleles expected for a lower sample size. In our

case, we estimated allelic richness standardised for rare-

faction to n = 16 (the smallest sample) using the software

FSTAT 2.9.3 (Goudet 2001). In addition, we calculated the

Queller and Goodnight (1989) index of genetic relatedness

for eight captive breeding pairs, using the program SPA-

GeDi (Hardy and Vekemans 2002).

For sperm velocity recordings, we collected fresh ejac-

ulates from eight polatzeki and nine teydea males actively

breeding in the Tafira recuperation center, Gran Canaria.

The ejaculates were immediately diluted in 30–60 ll

(depending on the size of the ejaculate to obtain an optimal

density of sperm for the analysis) of preheated Dulbecco’s

Modified Eagle Medium (advanced DMEM; Invitrogen,

CA, USA) and the tubes placed in a heating block set to

40 �C. Next, we carefully homogenised the solution using

a pipette and, within 20 s, 5.9 ll of the diluted sperm was

deposited on a preheated counting chamber (6 ll, 20 lm

depth, 2 chamber slide; Leja Products, Nieuw-Vennep,

Netherlands), mounted on a Hamilton Thorne MiniTherm

stage warmer set to 40 �C (Hamilton Thorne Biosciences,

Beverly, USA). Sperm motion was recorded using a mini-

DV camera (Sony HDR-HC1E) mounted on an upright

microscope (Olympus CX41) with a 94 objective. The

camera was set to 910 optical zoom and infinite focus. For

each male, we recorded 6 different viewing fields of the

counting chamber. Computer-assisted sperm analysis

(HTM-CEROS sperm tracker, CEROS v.12; Hamilton

Thorne Research) was used to analyse the recordings. The

sperm analyser was set at a frame rate of 50 Hz and 25

frames were analysed (i.e. sperm cells were tracked for

Table 1 Locus-specific details of the number of alleles (k), observed

(Ho) and expected (He) heterozygosity, estimated null-allele fre-

quency (Nulle), and population differentiation (FST) for the polatzeki(n = 16) and teydea (n = 27) Blue Chaffinches (Fringilla teydea)

Locus Population k Ho He Nulle FST

Ftey08 polatzeki 8 0.813 0.839 0.00 0.102***

teydea 21 0.778 0.915 0.07

Ftey19 polatzeki 3 0.563 0.667 0.06 0.248***

teydea 4 0.704 0.607 -0.08

Ftey20 polatzeki 6 0.313*** 0.738 0.40 0.342***

teydea 4 0.333*** 0.592 0.26

Ftey22 polatzeki 11 1.000 0.899 -0.07 0.070***

teydea 22 0.889 0.951 0.02

Ftey25 polatzeki 9 0.750 0.855 0.05 0.092***

teydea 24 0.556*** 0.950 0.26

Ftey28 polatzeki 10 0.875 0.877 -0.01 0.074***

teydea 25 0.815** 0.956 0.07

Ftey29 polatzeki 4 0.875 0.720 -0.11 0.661***

teydea 2 0.037 0.037 -0.00

Ftey30 polatzeki 3 0.625 0.615 -0.01 0.704***

teydea 1 0.000 0.000 –

Mean polatzeki 6.8 0.727 0.776 0.038 0.267***

teydea 12.9 0.514 0.626 0.086

Significant deviations from Hardy–Weinberg equilibrium are indi-

cated for Ho (** P \ 0.01, *** P \ 0.001)

J Ornithol

123

0.5 s). Each analysis was visually examined and cell

detection parameters adjusted to optimise the detection of

motile and static/drifting spermatozoa (minimum con-

trast = 80, minimum cell detection size = 10 pixels). The

output from CEROS gives average path velocity (VAP),

straight line velocity (VSL), and curvilinear velocity

(VCL) for individual sperm tracks. We chose to calculate

mean VCL as our measure of velocity, because it reflects

the actual frame-to-frame movement and thus the actual

velocity, and is directly comparable to other published

studies in passerine birds (e.g. Kleven et al. 2009). Sper-

matozoa with VAP \30 lms-1 and/or VSL \25 lms-1

were considered static or drifting and counted as non-

motile cells. They were excluded for calculations of

Fig. 1 Allele-size (bp) frequency distributions of eight microsatellite loci in Blue Chaffinches Fringilla teydea on Gran Canaria (ssp. polatzeki;blue columns) and Tenerife (ssp. teydea; red columns)

J Ornithol

123

velocity (VCL) along with spermatozoa tracked for less

than 10 frames. We also removed any tracks with

straightness score below 70 or linearity score below 40, and

tracks for which the maximum frame-to-frame movement

exceeded the average frame-to-frame movement by 4 SDs

for the same track, as such tracks tended to represent

tracking errors in the software. Statistical tests of differ-

ences between subspecies in the proportion of motile cells

and in VCL accounted for variation in the number of sperm

cells scored per bird. For the test of difference in propor-

tion motile cells, we applied a generalised linear model

(GLM) with the number of motile cells as nominator, the

total number of cells as denominator, a binomial error

structure, and a logit link function, using the glm function

in the software R v.2.15.1 (R Development Core Team

2010). For the test of difference in VCL, we applied a

linear mixed model fit with REML, with individual sperm

tracks nested within males, using the lmer function in the

lme4 R library. Other statistical tests were carried out in

Statistica v.7.1 (StatSoft).

Results

The microsatellite genotyping of the 16 polatzeki and the

27 teydea individuals revealed some marked differences in

allele size distributions and variability across the eight loci.

The basic locus statistics are given in Table 1, and allele

sizes (bp) and their frequency distributions are visualised

for each marker in Fig. 1. In teydea, one marker (Ftey30)

was monomorphic while four others had more than 20

alleles each. In polatzeki, the maximum number of alleles

per locus was only 11 (Ftey22), but none were monomor-

phic. The two taxa showed significant differences in allele

frequency distributions in each of the eight microsatellites

as indicated by high FST values (Table 1). In the four most

polymorphic loci (Fig. 1, left panels), teydea generally had

more alleles than polatzeki and they spanned a wider size

range. In the four other loci where both taxa had relatively

few alleles (Fig. 1, right panels), polatzeki typically had

larger alleles than teydea. There were, however, significant

deviations from Hardy–Weinberg equilibrium for one locus

in polatzeki and for three loci in teydea (Table 1), which is

reflected in lower observed than expected heterozygosities

and a relatively high estimate of null alleles for these loci.

FST estimates were probably underestimated in these cases,

in particular for the markers Ftey25 and Ftey28 where null

alleles occurred only in teydea and are most likely different

from any of the genotyped polatzeki alleles. The overall

FST for all eight loci combined was calculated at

FST = 0.267 (P \ 0.001) for the two populations.

Summed over all loci, there were altogether 54 different

alleles among the 16 polatzeki individuals and 103 alleles

among the 27 teydea individuals (Table 1). The allelic

richness was on average 10.1 alleles per locus in teydea

compared with 6.8 alleles in polatzeki (Table 2; paired

t test: t7 = 1.75, P = 0.12). The lower mean allelic rich-

ness for polatzeki was mainly caused by a lower number of

alleles for the four most polymorphic markers (Ftey8,

Ftey22, Ftey25 and Ftey28; Fig. 2). This is as expected

from genetic bottleneck theory (Nei et al. 1975), because

more polymorphic loci have more low-frequency alleles,

which are more likely to be lost in a process of genetic

drift.

Allelic diversity in our polatzeki individuals was similar

to that in the wild-ranging population genotyped by Suarez

et al. (2012). Estimates of allelic richness on their dataset,

standardised to our sample size of n = 16, were 7.5 and 6.9

Table 2 Allelic diversity in eight microsatellite loci for the polatzeki (Gran Canaria) and teydea (Tenerife) Blue Chaffinches

Locus Number of alleles Allelic richness

Captive polatzeki(n = 16)

Wild teydea(n = 27)

Wild polatzekia

(n = 64)

Captive

polatzekiWild

teydeaWild polatzekia

(before)

Wild polatzekia

(after)

Ftey8 8 21 13 8.0 16.4 9.3 8.3

Ftey19 3 4 4 3.0 3.6 3.9 3.9

Ftey20 6 4 12 6.0 3.6 8.8 8.6

Ftey22 11 22 16 11.0 17.5 10.1 10.2

Ftey25 9 24 12 9.0 18.2 9.2 7.5

Ftey28 10 25 15 10.0 18.8 11.6 9.3

Ftey29 4 2 5 4.0 1.6 4.0 4.0

Ftey30 3 1 3 3.0 1.0 3.0 3.0

Mean 6.8 12.9 10.0 6.8 10.1 7.5 6.9

a Refer to data in Suarez et al. (2012) and are grouped into before (n = 32) and after (n = 32) the wildfires in 2007. All allelic richness estimates

were calculated for the minimum sample size of n = 16 (see ‘‘Methods’’)

J Ornithol

123

alleles per locus, before and after the 2007 wildfires,

respectively, and comparable to 6.8 alleles per locus for our

captive birds (Table 2; captive polatzeki vs. wild polatzeki

before the wildfires: paired t7 = 1.79, P = 0.12, captive

polatzeki vs. wild polatzeki after the wildfires: paired

t7 = 0.20, P = 0.85).

Furthermore, there was no evidence of close inbreeding

among the wild-caught polatzeki birds used in the captive

breeding programme. We calculated the Queller and

Goodnight (1989) index of genetic relatedness for the eight

pairs, using the program SPAGeDi (Hardy and Vekemans

2002). The index ranges from -1 (completely dissimilar)

to 1 (completely similar), with a value of 0 expected under

random combination of alleles. The eight pairs had an

average relatedness score of 0.015 ± 0.27 SD, which was

similar to the relatedness score for all other possible

combinations of adults (0.021 ± 0.24; t7 = 0.06,

P = 0.95). Mean heterozygosity (average proportion of

heterozygous loci) for the 16 adults was 0.727 ± 0.178. In

comparison, 19 offspring produced in captivity had a mean

heterozygosity of 0.717 ± 0.100, which was not signifi-

cantly different from the parents (Mann–Whitney U test:

Z = 0.414, n1 = 16, n2 = 19, P = 0.68). The inbreeding

coefficient, FIS, calculated for all loci combined for the 16

adults, was slightly positive (FIS = 0.066), but not signif-

icantly different from zero (P = 0.090). The same ten-

dency of slightly positive FIS values was reported by

Suarez et al. (2012) for the wild polatzeki population.

The computer-assisted sperm analyses (CASA) of fresh

ejaculates showed that polatzeki males had significantly

lower proportions of motile sperm cells than teydea males

(0.21 ± 0.17 vs. 0.34 ± 0.15; Table 3), and that the motile

cells swam at a significantly lower speed (122.1 ± 27.6 vs.

171.8 ± 39.5 lm s-1; Table 3). The mean numbers of

tracked cells per ejaculate are also given in Table 3, but

because ejaculates were diluted differentially in order to

obtain an optimal sperm density for CASA, they do not

directly reflect sperm counts. However, ejaculates of

polatzeki were generally larger and therefore diluted more

than those of teydea, so the significant difference in the

number of sperm tracks should actually indicate higher

sperm counts in polatzeki than in teydea.

Discussion

The microsatellite analyses indicated that the polatzeki and

teydea subspecies of the Blue Chaffinch are significantly

differentiated in nuclear DNA. This divergence is likely to

be the result of two sources of evolutionary change, i.e.

mutations and genetic drift. First, the two taxa have a long

history of independent allopatric evolution, as indicated by

their deep divergence and complete lineage sorting of their

mtDNA (Pestano et al. 2000). As microsatelittes have

relatively high mutation rates (Li et al. 2002), shifts in their

allele size distributions, as we observed, might also be

expected in an evolutionary time scale. For example,

marked differences in allele sizes of a hypervariable

microsatellite have been documented for six species of

swallows (Anmarkrud et al. 2011). Second, the polatzeki

population has recently undergone a severe demographic

bottleneck, which may have caused a significant loss of

genetic diversity, especially rare alleles (Nei et al. 1975).

There are two lines of evidence in our results for a

genetic bottleneck in polatzeki. First, the actual microsat-

ellite loci were derived from polatzeki (Suarez et al. 2009).

There is a general trend that heterologous microsatellites

become less variable as phylogenetic distance from the

species of origin increases (Primmer et al. 1996). We

found, contrary to expectation from this pattern, that teydea

had more alleles than polatzeki. This would indicate that

the ancestral polatzeki population harboured more alleles.

Secondly, we found that allelic diversity in polatzeki was

reduced primarily in the most polymorphic loci, which had

many low-frequency alleles in teydea. Such alleles are

more likely to be lost in demographic bottlenecks (Nei

et al. 1975; Spencer et al. 2000; Leberg 2002).

We also found that polatzeki males had significantly

lower sperm motility than teydea males. The proportion

motile cells for polatzeki (0.21) was very low compared to

the scores we have obtained for other passerine species. For

example, we have recorded a mean proportion of motile

sperm of 0.51 in the sister species, the Common Chaffinch

(Fringilla coelebs), which has very similar sperm mor-

phology (own unpublished data). In general, mean pro-

portion of motile cells in wild passerines lie within the

range of 0.40–0.90 (own unpublished data,[10 species). It

Fig. 2 Allelic richness estimates for eight microsatellite loci in Blue

Chaffinches on Gran Canaria (ssp. polatzeki) and Tenerife (ssp.

teydea). The diagonal line indicates y = x, i.e. the expectation of

equal allelic richness in the two populations

J Ornithol

123

should be noted, however, that the swimming speed

recorded in both polatzeki (mean VCL of 122 lms-1) and

teydea (mean VCL of 172 lms-1) are not particularly low

when compared to other passerine species. For example,

mean VCL estimates ranged from 77 to 167 lms-1 among

42 species (Kleven et al. 2009). Therefore, the difference in

VCL estimates between the two Blue Chaffinch taxa does

not necessarily imply a difference in sperm quality. Nev-

ertheless, the reduced sperm motility in polatzeki males is

of significant concern, because there are reports from

mammalian taxa that sperm quality and performance are

susceptible to reduced genetic diversity and inbreeding

depression (Gage et al. 2006; Fitzpatrick and Evans 2009).

To our knowledge, a similar effect has not yet been dem-

onstrated for birds.

We conclude that the two Blue Chaffinch taxa, although

not currently recognized as separate species, qualify for

ESU status (sensu Moritz 1994), because they are signifi-

cantly differentiated in both mtDNA (Pestano et al. 2000)

and nuclear markers (this study). The polatzeki population

should be considered a critically endangered ESU and

conservation authorities should act to reduce its risk of

extinction. There is an urgent need for a population via-

bility analysis (Beissinger and McCullough 2002), includ-

ing a thorough screening of functional genetic diversity and

fertility in the wild. Our study has indicated that neutral

genetic diversity is reduced, presumably as a result of the

severe decline in population size over the last century. It is,

however, difficult to predict how loss of neutral genetic

diversity affects individual fitness and extinction risk of a

population (Jamieson 2007). But, regardless of any

inbreeding consequences, it is obvious that the polatzeki

population is critically threatened by extinction from sto-

chastic variation in population size alone. We would

therefore recommend maintaining the captive population,

both for supplementing the wild population and for keeping

a back-up breeding stock, should the small remnant pop-

ulation go extinct.

Acknowledgments We thank Jostein Gohli and Even Stensrud for

assistance in the field on Tenerife, and Becky Cramer, Melissah Rowe

and two anonymous referees for comments. Financial support was

received from the Research Council of Norway. Permits for blood and

sperm sampling were issued by Excmo. Cabildo de Tenerife and the

Canarian Government. The experimental work complies with the

current laws of Spain and Norway.

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