Discriminating woody species assemblages from National Forest Inventory data based on phylogeny in Georgia

Classifications of forest vegetation types and characterization of related species assemblages are important analytical tools for mapping and diversity monitoring of forest communities. The discrimination of forest communities is often based on β-diversity, which can be quantified via numerous indices to derive compositional dissimilarity between samples. This study aims to evaluate the applicability of unsupervised classification for National Forest Inventory data from Georgia by comparing two cluster hierarchies. We calculated the mean basal area per hectare for each woody species across 1059 plot observations and quantified interspecies distances for all 87 species. Following an unspuervised cluster analysis, we compared the results derived from the species-neutral dissimilarity (Bray-Curtis) with those based on the Discriminating Avalanche dissimilarity, which incorporates interspecies phylogenetic variation. Incorporating genetic variation in the dissimilarity quantification resulted in a more nuanced discrimination of woody species assemblages and increased cluster coherence. Favorable statistics include the total number of clusters (23 vs. 20), mean distance within clusters (0.773 vs. 0.343), and within sum of squares (344.13 vs. 112.92). Clusters derived from dissimilarities that account for genetic variation showed a more robust alignment with biogeographical units, such as elevation and known habitats. We demonstrate that the applicability of unsupervised classification of species assemblages to large-scale forest inventory data strongly depends on the underlying quantification of dissimilarity. Our results indicate that by incorporating phylogenetic variation, a more precise classification aligned with biogeographic units is attained. This supports the concept that the genetic signal of species assemblages reflects biogeographical patterns and facilitates more precise analyses for mapping, monitoring, and management of forest diversity.

Unveiling a hotspot of genetic diversity in southern Italy for the endangered Hermann’s tortoise Testudo hermanni

Background

Hotspots of intraspecific genetic diversity represent invaluable resources for species to cope with environmental changes, and their identification is increasingly recognized as a major goal of conservation ecology research. However, even for iconic and endangered species, conservation strategies are often planned without thorough information on the geographic patterns of genetic variation. Here, we investigated the spatial patterns of genetic variation of the endangered Hermann’s tortoise Testudo hermanni in the Italian Peninsula by genotyping 174 individuals at 7 microsatellite loci, with the aim to contribute to planning effective conservation strategies.

Results

Ordination-based and Bayesian clustering analyses consistently identified three main genetic clusters, one spread in the central and northern part of the peninsula, and two restricted to southern Italy and Sicily, respectively. The highest levels of genetic diversity were found in populations of the southern cluster and, in particular, at the northern edges of its distribution (He > 0.6, Ar > 2.8 ), that correspond to areas of putative secondary contact and admixture between distinct lineages. Our results clearly identify a hotspot of genetic diversity for the Hermann’s tortoise in southern Italy.

Conclusion

We inferred the evolutionary history and the spatial patterns of genetic variation of the Hermann’s tortoise in the Italian Peninsula. We identified three main genetic clusters along the peninsula and a hotspot of intraspecific diversity in southern Italy. Our results underline the urgent need for conservation actions to warrant the long-term persistence of viable tortoise populations in this area. Furthrmore, these data add further evidence to the role of southern Italy as a biodiversity hotspot for temperate fauna, claiming for higher consideration of this area in large scale conservation programs.

Distribution and conservation status of threatened endemic amphibians within the Aspromonte mountain region, a hotspot of Mediterranean biodiversity

Amphibian biodiversity loss in recent years has exceeded that of all other groups of vertebrates. In this context, biodiversity hotspots represent priority targets for conservation in amphibian populations. However, little information is available on the distribution and conservation status of amphibian species within most biodiversity hotspots. Here, we characterized the distribution and conservation status of four threatened endemic amphibians (Bombina pachypus, Salamandra salamandra gigliolii, Salamandrina terdigitata, and Rana italica) in the Aspromonte Mountain region, a biodiversity hotspot in southern Italy where the conservation status of amphibians is almost unexplored. We conducted an intensive field survey of 507 potential breeding sites spanning over 2,326 km2. We found that all four species were widespread in the study area. We observed 337 species occurrences: 63 for S. s. gigliolii, 29 for S. terdigitata, 84 for B. pachypus, and 161 for R. italica. Species distribution analysis revealed that S. s. gigliolii and R. italica populations had an extended and homogenous distribution. Conversely, S. terdigitata showed a dispersed pattern, with long distances among breeding sites, and B. pachypus an aggregated pattern, associated with the availability of suitable artificial habitats. On the other hand, we reported a decrease in B. pachypus occurrence in its natural habitats, which reflects a negative trend of its populations. Overall, our results provide an encouraging framework for the conservation of amphibian populations in this area, but highlight the low coverage of threatened amphibian populations in protected areas, highlighting the need for a reassessment of conservation policies and spatial conservation planning for the Aspromonte region.

Verification of hotspots of genetic diversity in Korean population of Grateloupia asiatica and G. jejuensis (Rhodophyta) show low genetic diversity and similar geographic distribution

BACKGROUND

Understanding the genetic diversity and distribution patterns of seaweeds species is crucial for evaluating key regions of high genetic diversity. Identifying hotspots of high intraspecific diversity is an important step for developing conservation strategies. Grateloupia is a diverse genus of Rhodophyta, many of which are resource of numerous useful bioactive compounds; therefore, the genus is valuable target for conservation.

OBJECTIVE

The aim of this study is to examine the genetic diversity and population structure of two Grateloupia species, Grateloupia asiatica and Grateloupia jejuensis, with the understanding of the phylogeography of the Korean genetic diversity hotspot for two species.

METHODS

Plastid rbcL gene sequences of 134 specimens of G. asiatica and 112 specimens of G. jejuensis collected from the Korean coast were analyzed. We evaluated the number of haplotypes, genetic diversity (haplotype and nucleotide diversity), and haplotype networks of two species. Historical demographic was inferred by calculating neutrality tests and genetic differentiation was estimated using the fixation index, F_ST.

RESULTS

Our results show that both species are generally similar in geographical distribution patterns, that is, relatively homogeneous with few haplotypes derived from the most frequent haplotype. The east coast of Korea is identified as a 'hotspot' with the highest genetic diversity for both species, whereas Jeju Island is identified as a 'cold spot' with the lowest genetic diversity for G. jejuensis. Analyses across most distribution ranges of the two species in Korea reveal low genetic and haplotype diversities, which could indicate that these two Grateloupia species have either experienced a historical lack of diversity or a recent reduction in diversity due to high gene flow.

CONCLUSIONS

The low genetic diversity values found in the present study raise considerable concern about the conservation status of these two Grateloupia species and highlight the need to locate further hotspots of genetic diversity to strengthen their resilience against further decline.

Reconstructing hotspots of genetic diversity from glacial refugia and subsequent dispersal in Italian common toads (Bufo bufo)

Genetic diversity feeds the evolutionary process and allows populations to adapt to environmental changes. However, we still lack a thorough understanding of why hotspots of genetic diversity are so 'hot'. Here, we analysed the relative contribution of bioclimatic stability and genetic admixture between divergent lineages in shaping spatial patterns of genetic diversity in the common toad Bufo bufo along the Italian peninsula. We combined population genetic, phylogeographic and species distribution modelling (SDM) approaches to map ancestral areas, glacial refugia, and secondary contact zones. We consistently identified three phylogeographic lineages, distributed in northern, central and southern Italy. These lineages expanded from their ancestral areas and established secondary contact zones, before the last interglacial. SDM identified widespread glacial refugia in peninsular Italy, sometimes located under the present-day sea-level. Generalized linear models indicated genetic admixture as the only significant predictor of the levels of population genetic diversity. Our results show that glacial refugia contributed to preserving both levels and patterns of genetic diversity across glacial-interglacial cycles, but not to their formation, and highlight a general principle emerging in Mediterranean species: higher levels of genetic diversity mark populations with substantial contributions from multiple genetic lineages, irrespective of the location of glacial refugia.