Aline Finger

Forest fragmentation genetics in a formerly widespread island endemic tree: Vateriopsis seychellarum (Dipterocarpaceae)

Habitat fragmentation and changed land use have seriously reduced population size in many tropical forest tree species. Formerly widespread species with limited gene flow may be particularly vulnerable to the negative genetic effects of forest fragmentation and small population size. Vateriopsis seychellarum (Dipterocarpaceae) is a formerly widespread canopy tree of the Seychelles, but is now reduced to 132 adult individuals distributed in eleven sites. Using ten microsatellite loci, a genetic inventory of all adult trees and a sample of 317 progeny, we demonstrate that despite its restricted range, overall genetic diversity was relatively high (HE: 0.56). The juvenile cohort, however, had significantly lower allelic richness (adults RS: 3.91; juveniles RS: 2.83) and observed heterozygosity than adult trees (adults HO: 0.62; juveniles HO: 0.48). Rare alleles were fewer and kinship between individuals was stronger in juveniles. Significant fine‐scale spatial genetic structure was observed in remnant adults, and parentage analysis indicated that more than 90% of sampled progeny disperse <25 m and pollen dispersed <50 m. The molecular data confirmed that two populations were derived entirely from self‐fertilized offspring from a single surviving mother tree. These populations produce viable offspring. Despite this extreme genetic bottleneck, self‐compatibility may provide V. seychellarum with some resistance to the genetic consequences of habitat fragmentation, at least in the short term. We discuss our findings in the context of other rare and threatened dipterocarp species which are vulnerable to miss‐management of genetic resources and population fragmentation.

Back from the brink: potential for genetic rescue in a critically endangered tree.

Rare plant species are vulnerable to genetic erosion and inbreeding associated with small population size and isolation due to increasing habitat fragmentation. The degree to which these problems undermine population viability remains debated. We explore genetic and reproductive processes in the critically endangered long‐lived tropical tree Medusagyne oppositifolia, an endemic to the Seychelles with a naturally patchy distribution. This species is failing to recruit in three of its four populations. We evaluate whether recruitment failure is linked to genetic problems associated with fragmentation, and if genetic rescue can mitigate such problems. Medusagyne oppositifolia comprises 90 extant trees in four populations, with only the largest (78 trees) having successful recruitment. Using 10 microsatellite loci, we demonstrated that genetic diversity is high (HE: 0.48–0.63; HO: 0.56–0.78) in three populations, with only the smallest population having relatively low diversity (HE: 0.26 and HO: 0.30). All populations have unique alleles, high genetic differentiation, and significant within population structure. Pollen and seed dispersal distances were mostly less than 100 m. Individuals in small populations were more related than individuals in the large population, thus inbreeding might explain recruitment failure in small populations. Indeed, inter‐population pollination crosses from the large donor population to a small recipient population resulted in higher reproductive success relative to within‐population crosses. Our study highlights the importance of maintaining gene flow between populations even in species that have naturally patchy distributions. We demonstrate the potential for genetic and ecological rescue to support conservation of plant species with limited gene flow.

Unprecedented long-term genetic monomorphism in an endangered relict butterfly species

Multi-locus monomorphism in microsatellites is practically non-existent, with one notable exception, the island fox (Urocyon littoralis dickeyi) population on San Nicolas island off the coast of southern California, having been called “the most monomorphic sexually reproducing animal population yet reported”. Here, we present the unprecedented long-term monomorphism in relict populations of the highly endangered Parnassius apollo butterfly, which is protected by CITES and classified as “threatened” by the IUCN. The species is disjunctly distributed throughout the western Palaearctic and has occurred in several small remnant populations outside its main distribution area. We screened 78 individuals from 1 such relict area (Mosel valley, Germany) at 16 allozyme and 6 microsatellite loci with the latter known to be polymorphic in this species elsewhere. From the same area, we also genotyped 55 museum specimens sampled from 1895 to 1989 to compare historical and present levels of genetic diversity. However, none of all these temporal populations yielded any polymorphism. Thus, present and historical butterflies were completely monomorphic for the same fixed allele. This is the second study to report multi-locus monomorphism for microsatellites in an animal population and the first one to prove this monomorphism not to be the consequence of recent factors. Possible explanations for our results are a very low long-term effective population size and/or a strong historic bottleneck or founder event. Since the studied population has just recovered from a recent population breakdown (second half of twentieth century) and no signs of inbreeding depression have been detected, natural selection might have purged the population of weakly deleterious alleles, thus rendering it less susceptible to the usual negative corollaries of high levels of homozygosity and low effective population size.

The relevance of time series in molecular ecology and conservation biology

The genetic structure of a species is shaped by the interaction of contemporary and historical factors. Analyses of individuals from the same population sampled at different points in time can help to disentangle the effects of current and historical forces and facilitate the understanding of the forces driving the differentiation of populations. The use of such time series allows for the exploration of changes at the population and intraspecific levels over time. Material from museum collections plays a key role in understanding and evaluating observed population structures, especially if large numbers of individuals have been sampled from the same locations at multiple time points. In these cases, changes in population structure can be assessed empirically. The development of new molecular markers relying on short DNA fragments (such as microsatellites or single nucleotide polymorphisms) allows for the analysis of long‐preserved and partially degraded samples. Recently developed techniques to construct genome libraries with a reduced complexity and next generation sequencing and their associated analysis pipelines have the potential to facilitate marker development and genotyping in non‐model species. In this review, we discuss the problems with sampling and available marker systems for historical specimens and demonstrate that temporal comparative studies are crucial for the estimation of important population genetic parameters and to measure empirically the effects of recent habitat alteration. While many of these analyses can be performed with samples taken at a single point in time, the measurements are more robust if multiple points in time are studied. Furthermore, examining the effects of habitat alteration, population declines, and population bottlenecks is only possible if samples before and after the respective events are included.

Genetic Connectivity of the Moth Pollinated Tree Glionnetia sericea in a Highly Fragmented Habitat

Long-distance gene flow is thought to be one prerequisite for the persistence of plant species in fragmented environments. Human influences have led to severe fragmentation of native habitats in the Seychelles islands, with many species surviving only in small and isolated populations. The endangered Seychelles endemic tree Glionnetia sericea is restricted to altitudes between 450 m and 900 m where the native forest vegetation has been largely lost and replaced with exotic invasives over the last 200 years. This study explores the genetic and ecological consequences of population fragmentation in this species by analysing patterns of genetic diversity in a sample of adults, juveniles and seeds, and by using controlled pollination experiments. Our results show no decrease in genetic diversity and no increase in genetic structuring from adult to juvenile cohorts. Despite significant inbreeding in some populations, there is no evidence of higher inbreeding in juvenile cohorts relative to adults. A Bayesian structure analysis and a tentative paternity analysis indicate extensive historical and contemporary gene flow among remnant populations. Pollination experiments and a paternity analysis show that Glionnetia sericea is self-compatible. Nevertheless, outcrossing is present with 7% of mating events resulting from pollen transfer between populations. Artificial pollination provided no evidence for pollen limitation in isolated populations. The highly mobile and specialized hawkmoth pollinators (Agrius convolvuli and Cenophodes tamsi; Sphingidae) appear to promote extensive gene flow, thus mitigating the potential negative ecological and genetic effects of habitat fragmentation in this species. We conclude that contemporary gene flow is sufficient to maintain genetic connectivity in this rare and restricted Seychelles endemic, in contrast to other island endemic tree species with limited contemporary gene flow.

Hidden in plain view: Cryptic diversity in the emblematic Araucaria of New Caledonia

PREMISE OF THE STUDY Cryptic species represent a conservation challenge, because distributions and threats cannot be accurately assessed until species are recognized and defined. Cryptic species are common in diminutive and morphologically simple organisms, but are rare in charismatic and/or highly visible groups such as conifers. New Caledonia, a small island in the southern Pacific is a hotspot of diversity for the emblematic conifer genus Araucaria (Araucariaceae, Monkey Puzzle trees) where 13 of the 19 recognized species are endemic. METHODS We sampled across the entire geographical distribution of two closely related species (Araucaria rulei and A. muelleri) and screened them for genetic variation at 12 nuclear and 14 plastid microsatellites and one plastid minisatellite; a subset of the samples was also examined using leaf morphometrics. KEY RESULTS The genetic data show that populations of the endangered A. muelleri fall into two clearly distinct genetic groups: one corresponding to montane populations, the other corresponding to trees from lower elevation populations from around the Goro plateau. These Goro plateau populations are more closely related to A. rulei, but are sufficiently genetically and morphological distinct to warrant recognition as a new species. CONCLUSIONS Our study shows the presence of a previously unrecognized species in this flagship group, and that A. muelleri has 30% fewer individuals than previously thought. Combined, this clarification of species diversity and distributions provides important information to aid conservation planning for New Caledonian Araucaria.

Fragmentation genetics in the tropics

On the 23rd of February, some 50 Conservation Geneticists from around the global gathered for a half day symposium entitled ‘Fragmentation Genetics in the Tropics’ held at the Friedrich-Alexander University, Erlangen, Germany as part of the German Tropical Ecology Society annual meeting 2012. The overall aim of this symposium was to showcase the latest novel research applying molecular methods (landscape genetics, conservation genetics and phylogeography) to advance our understanding of genetic consequences of fragmentation in the tropics, particularly in the context of how population size and isolation influences population and species extinction. I provide a brief overview of the symposium and finish with a call for papers for a special issue of the sister journal Conservation Genetics, for which submission is now open.

Development of thirteen polymorphic microsatellite markers for the Seychelles endangered and endemic jellyfish tree Medusagyne oppositifolia (Medusagynaceae)

The jellyfish tree Medusagyne oppositifolia is a flagship species of the Seychelles, being not only extremely rare and critically endangered, but also representing a monospecific endemic family, Medusagynaceae. The species survives in four populations on the Island of Mahé, where the total number of reproductive adults is 89. Natural regeneration is only known for the largest of these populations. Understanding the mechanisms driving the lack of natural regeneration in this species has great conservation relevance. We developed thirteen polymorphic microsatellite loci for this species to enable studies of historic and contemporary gene flow. The number of alleles per locus ranged from 2 to 15 (mean of 6.62 per locus) with an average polymorphic information content of 0.54 across loci. Expected heterozygosity ranged from 0.12 to 0.66 with only two of the 13 loci showing deviation from Hardy–Weinberg expectation. The markers will help to provide a better understanding of the significance of historic distributions, gene flow and recent anthropogenic habitat degradation for the in situ and ex-situ conservation of this flagship tree species.