Habitat fragmentation, i.e., fragment size and isolation, can differentially alter patterns of neutral and quantitative genetic variation, fitness and phenotypic plasticity of plant populations, but their effects have rarely been tested simultaneously. We assessed the combined effects of size and connectivity on these aspects of genetic and phenotypic variation in populations of Centaurea hyssopifolia, a narrow endemic gypsophile that previously showed performance differences associated with fragmentation. We grew 111 maternal families sampled from ten populations that differed in their fragment size and connectivity in a common garden, and characterized quantitative genetic variation, phenotypic plasticity to drought for key functional traits, and plant survival, as a measure of population fitness. We also assessed neutral genetic variation within and among populations using eight microsatellite markers. Although Centaurea hyssopifolia is a narrow endemic gypsophile, we found substantial neutral genetic variation and quantitative variation for key functional traits. The partition of genetic variance indicated that a higher proportion of variation was found within populations, which is also consistent with low population differentiation in molecular markers, functional traits and their plasticity. This, combined with the generally small effect of habitat fragmentation suggests that gene flow among populations is not restricted, despite large differences in fragment size and isolation. Importantly, population’s similarities in genetic variation and plasticity did not reflect the lower survival observed in isolated populations. Overall, our results indicate that, although the species consists of genetically variable populations able to express functional plasticity, such aspects of adaptive potential may not always reflect populations’ survival. Given the differential effects of habitat connectivity on functional traits, genetic variation and fitness, our study highlights the need to shift the focus of fragmentation studies to the mechanisms that regulate connectivity effects, and call for caution on the use of genetic variation and plasticity to forecast population performance.

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Habitat Fragmentation Differentially Affects Genetic Variation, Phenotypic Plasticity and Survival in Populations of a Gypsum Endemic.

Habitat fragmentation is a major threat to the maintenance of genetic diversity in many plant populations. Genetic effects of population size have received far more attention than the effects of isolation—or connectivity—but both are key components of the fragmentation process. To analyze the consequences of fragment size and connectivity on the neutral genetic variation and population genetic structure of the dominant gypsophile Lepidium subulatum, we selected 20 fragments along two continuous gradients of size and degree of isolation in a fragmented gypsum landscape of Central Spain. We used eight polymorphic microsatellite markers, and analyzed a total of 344 individuals. Populations were characterized by high levels of genetic diversity and low inbreeding coefficients, which agrees with the mainly outcrossing system of L. subulatum and its high abundance in gypsum landscapes. Bayesian clustering methods, pairwise F
 ST values and analysis of molecular variance revealed low among-population differentiation, with no significant isolation by distance. However, several genetic diversity indices such as allelic richness, number of effective alleles, expected heterozygosity and number of private alleles were negatively related to population isolation. The higher genetic diversity found on more connected fragments suggests higher rates of gene flow among more connected populations. Overall, our results highlight that fragmentation can have important effects on intra-population genetic processes even for locally abundant, dominant species. This, together with previously documented effects of connectivity on fitness of gypsophile species highlights the importance of including habitat connectivity in management and conservation strategies of this type of semiarid systems.

Does higher connectivity lead to higher genetic diversity? Effects of habitat fragmentation on genetic variation and population structure in a gypsophile

The identification of areas of endemism is a crucial tool for both the interpretation of the spatial component of biological evolution and the plotting of priority areas as far as biodiversity conservation is concerned. Geographical isolation, aridity and special substrates are among the factors which can help to explain the restricted areas of the taxa. All these factors concur in the origin of the Iberian gypsophilous flora, rich in endemic and threatened species. Gypsum is a particularly demanding rock for plants, and gypsum outcrops are usually fragmented in space, in territories with arid conditions. Information on the presence of 71 gypsophytes was collected in 10 × 10 km Universal Transverse Mercator (UTM). The distribution of these plants was used to plot the main areas of endemism for the vascular flora on Iberian gypsum outcrops. This was carried out using the eNDeMism/Visor of eNDeMism (NDM/VNDM) program and several grid cell sizes. A total of 51 areas of endemicity were identified and represen...

Areas of endemism as a conservation criterion for Iberian gypsophilous flora: a multi-scale test using the NDM/VNDM program

Genetic and morphologic diversity of European fan palm (Chamaerops humilis L.) populations from different environments from Sicily

Variability, genetic structure and phylogeography of the dolomitophilous species Convolvulus boissieri (Convolvulaceae) in the Baetic ranges, inferred from AFLPs, plastid DNA and ITS sequences

Genetic diversity, genetic structure and phylogeography of the Iberian endemic Gypsophila struthium (Caryophyllaceae) as revealed by AFLP and plastid DNA sequences: connecting habitat fragmentation and diversification

To be considered “sustainable”, a city must be built with materials whose extraction and processing are not very aggressive with the environment and its ecological footprint palliated as much as possible. One of the materials most used in construction is the plaster. The gypsum outcrops, although traditionally have been poorly valued, have geomorphological and especially floristic values. In fact, to the point that the bushes that are developed on them have been declared priority habitats No. 1520 of the EU.

Towards an Eco-Compatible Origin of Construction Materials. Case Study: Gypsum

Biodiversity Conservation is a priority issue for the scientific community, and a main subject in the Biology and Geology curriculum at secondary school level in Spanish Educational System. In the present didactic proposal, we use the demographic monitoring of an endangered plant species to illustrate a research tool for estimates of biodiversity loos in nature, the local endemic Astragalus tremolsianus Pau. The aim of the proposal is to bring students closer to a real experience, which brings together knowledge of Biology, Algebra and Trigonometry, through Information and Communication Technologies (ICTs). Showing a census to monitor the populations of a threatened high mountain flora species into the classroom is an innovative teaching activity that combines and uses knowledge from different disciplines, as well as demonstrating a real application of the knowledge acquired. The use of mathematical tools encompasses a number of skills that require the application of mathematical principles and processes in the scientific context. The introduction of the structure of scientific texts is another positive aspect of this didactic experience. 

Encarnación Merlo

Papers

Genetic diversity, genetic structure and phylogeography of the Iberian endemic Gypsophila struthium (Caryophyllaceae) as revealed by AFLP and plastid DNA sequences: connecting habitat fragmentation and diversification

Towards an Eco-Compatible Origin of Construction Materials. Case Study: Gypsum

Proposal for Didactic Innovation through the Monitoring of Threatened Biodiversity