Morphological consequences of range fragmentation and population decline on the endangered Iberian lynx (Lynx pardinus)

Abstract

The Iberian lynx Lynx pardinus is one of the world's most endangered felids and is vulnerable to human-induced mortality and habitat loss, which reduce population size and accelerate the loss of genetic variation. Twenty-five metric traits of Iberian lynx skulls have been measured on 95 skulls collected between 1872 and 2003. The skulls belong to three geographically distinct areas/populations, which have recently diverged from each other as a consequence of increased habitat fragmentation: Do˜nana area, Sierra Morena mountains and Montes de Toledo area. The morphometric study was undertaken using univariate, multivariate and admixture analysis approaches, and all three techniques provided evidence for morphometric differentiation, both in skull size and shape, among the three populations for both males and females. Environmental and genetic forces that may have shaped these patterns are discussed. The males of the population of the Do˜nana area showed a different degree of reduction in size in nine of the skull traits with time, which has been suggested to be partly because of worsened habitat conditions. However, the heterogeneity of the degree of mean size reduction and the relatively high degree of reduction of some of the skull traits investigated (44%), which have altered the original proportions between the skull variables, could also partly be attributed to inbreeding depression in the Do˜nana population. The phenotypic variability of the skull traits showed significant increases (two traits) or decreases (nine traits) with time, and this different pattern of change with time has been suggested to be because of a different number of genes controlling the traits with different degrees of dominance and epistatic interactions. The increased phenotypic variability of two of the traits has also been attributed to a possible decreased level of developmental stability, which can be produced by environmental and/or genetic stress. The findings of this investigation contribute to the discussion about the utility and the limits of quantitative genetics techniques for conservation purposes.

Genotypic and phenotypic consequences of reintroduction history in the black-footed ferret (Mustela nigripes)

“…For these populations, monitoring changes in morphometric traits may provide an indirect measure of the phenotypic effects of inbreeding, because increased genetic load and reduced overdominance can affect morphological features (DeRose and Roff 1999). A negative correlation between body size and inbreeding has been found in such species as Iberian lynx (Lynx pardinus, Pertoldi et al 2006) and the endangered Mexican wolf (C. lupus baileyi, Fredrickson and Hedrick 2002).…”

A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect?

“…Once all these checks have been performed on the samples which are being compared for differences in the degree of fluctuating asymmetry, we believe that fluctuating asymmetry remains a powerful tool for comparing the level of developmental instability of samples. The methodology proposed in [37,40] can clearly also be utilized for the detection of the presence of genetic substructuring and in this case fluctuating asymmetry can be utilized for the detection of genetic and environmental stress in sexually reproducing populations which expands its application in the field of conservation biology in wild populations.…”

“…However even with this correction we should be aware of confounding factors, such as the standard error of the variance and the presence of mixtures due to environmental variability, which can produce platykurtic or leptokurtic distributions of the (r − l) values [35][36][37][38][39][40]. Mixtures due to genetic substructuring can also produce the same effects that environmental variability can have on the distribution of (r − l) values [41].…”

“…The absence of genetic substructure is allowing us to exclude one of the potential biases which is afflicting the fluctuating asymmetry indexes. In addition, following the methodology proposed in [21,37,40], it will be possible to exclude samples in an investigation where the presence of environmental variability and/or antisymmetry/directional asymmetry have been detected. Once all these checks have been performed on the samples which are being compared for differences in the degree of fluctuating asymmetry, we believe that fluctuating asymmetry remains a powerful tool for comparing the level of developmental instability of samples.…”

Developmental instability as an estimator of genetic stress

“…Such heterogeneity can, however, be detected by means of an admixture analysis, which will identify the presence of heterogeneity in the distribution of the trait or in the traits' (rÀl) distribution (Pertoldi et al, 2005b).…”