Does higher connectivity lead to higher genetic diversity? Effects of habitat fragmentation on genetic variation and population structure in a gypsophile
- 506 Downloads
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.
KeywordsHabitat fragmentation Connectivity Genetic diversity Population genetic structure Gypsophiles Microsatellite
We thank A. García-Fernández, M. Rodríguez, L. Concostrina-Zubiri, C. Díaz and G. Prieto-Porriños for their help during field and lab work, and especially A. Escudero and A. García-Fernández for their valuable comments and suggestions that contributed to improve the manuscript. Funding was provided by the British Ecological Society (research grant), the Spanish Association for terrestrial ecology (AEET, junior researcher grant), Remedinal-3 (S2013/MAE-2719) and the Juan de la Cierva Post-doctoral Program.
- Barrett SCH, Kohn JR, Falk DA, Holsinger KE (1991) Genetic and evolutionary consequences of small population size in plants: implications for conservation. In: Falk DA et al (eds) Genetics and conservation of rare plants. Oxford University Press, New York, pp 3–30Google Scholar
- Cornuet JM, Luikart G (1996a) Description and power analysis of genetic differentiation between populations. Genetics 163:367–374Google Scholar
- Hernández-Bermejo JE, Clemente M (1993) Lepidium. In: Castroviejo S et al (eds) Flora iberica cruciferae-monotropaceae. Real Jardín Botánico-CSIC, Madrid, pp 311–327Google Scholar
- Ihaka R, Gentleman R (1996) R: a language for data analysis and graphics. J Comput Graph Stat 5:299–314Google Scholar
- Leimu R, Vergeer P, Angeloni F, Ouborg NJ (2010) Habitat fragmentation, climate change, and inbreeding in plants. In: Ostfeld RS et al (eds) The year in ecology and conservation biology 2010. Wiley-Blackwell, New York, pp 84–98Google Scholar
- Lindenmayer DB, Fischer J (2006) Habitat fragmentation and landscape change. An ecological and conservation synthesis. Island Press, WashingtonGoogle Scholar
- Martínez-Nieto MI, Segarra-Moragues JG, Merlo ME, Martínez-Hernández F, Mota JF (2013) 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. Bot J Linn Soc 173:654–675CrossRefGoogle Scholar
- Oksanen J, Blanchet FG, Kindt R, Legendre P, Minchin PR, O’Hara RB, Simpson GL, Solymos P, Stevens MHH, Wagner H (2014) vegan: Community Ecology Package. R package version 2.3-2. https://CRAN.R-project.org/package=vegan
- Rivas-Martínez S, Costa M (1970) Comunidades gipsícolas del centro de España. Anales del Instituto Botánico A.J. Cavanilles 27:193–224Google Scholar
- Rzedowski J (1955) Notas sobre la flora y la vegetación del estado de San Luis Potosí. II. Estudio de diferencias florísticas y ecológicas condicionadas por ciertos tipos de sustrato geológico. Ciencia (México) 15:141–158Google Scholar
- Salmerón-Sánchez E, Martínez-Nieto MI, Martínez-Hernández F, Garrido-Becerra JA, Mendoza-Fernández AJ, Gil de Carrasco C, Ramos-Miras JJ, Lozano R, Merlo ME, Mota JF (2014) Ecology, genetic diversity and phylogeography of the Iberian endemic plant Jurinea pinnata (Lag.) DC. (Compositae) on two special edaphic substrates: dolomite and gypsum. Plant Soil 374:233–250CrossRefGoogle Scholar