Isozyme variability of the wetland specialistSwertia perennis(Gentianaceae) in relation to habitat size, isolation, and plant fitness

Abstract

We examined the effects of size and spatial isolation of fens on the isozyme variability of 17 populations of Swertia perennis. This long-lived perennial is a locally abundant fen specialist in Switzerland, where wetlands have been strongly fragmented. Isozyme variability was comparable to other outcrossing plants (A ϭ 1.53, AP p ϭ 2.01, P p ϭ 42.5, H o ϭ 0.113, H e ϭ 0.139). F statistics indicated both inbreeding within and differentiation between populations (F IS ϭ 0.076, F IT ϭ 0.194, F ST ϭ 0.128), with moderate gene flow between populations (N e m ϭ 1.703). Populations in small, isolated fens had reduced genetic variability and the highest withinpopulation inbreeding coefficients (F IS ). Isozyme variability was significantly associated with vegetative fitness traits (MANOVA), and the magnitude of leaf herbivory decreased as the percentage of polymorphic loci increased. These data suggest that the reduced genetic variability of S. perennis in small, isolated populations may reduce plant fitness, thereby increasing susceptibility to herbivore damage. Our study also shows that habitat fragmentation can reduce the genetic variability of populations of fairly common habitat specialists, which so far have attracted less conservation attention than rare species.

No Correlation Between Heterozygosity and Vegetative Fitness in the Narrow Endemic and Critically Endangered Clematis acerifolia (Ranunculaceae)

“…Likewise, the populations with higher levels of heterozygosity do not necessarily exhibit better performance. This pattern apparently contradicts the theoretical expectation of positive correlation between heterozygosity and fitness (Hansson and Westerberg 2002;Reed and Frankham 2003), which has been reported for several perennial plant taxa from western Europe, such as Swertia perennis for vegetative fitness (Lienert et al 2002) and Gentiana pneumonanthe (Oostermeijer et al 1994), Cochlearia bavarica (Paschke et al 2002), and Succisa pratensis (Vergeer et al 2003) for generative fitness. The possibility of a positive correlation between heterozygosity and fitness in Clematis acerifolia cannot be ruled out, however, because of the following considerations about the experimental conditions of our study.…”

Effects of habitat fragmentation on the fitness of two common wetland species, Carex davalliana and Succisa pratensis

“…In Succisa, we found a marginal significant differentiation (F st ) between populations in small habitat islands and main islands, which may be indicative of the selection for specific genotypes suggested in this study. Likewise in a formerly common fen meadow species, Swertia perennis, plant fitness and isozyme variability were significantly reduced in small isolated habitat islands (Lienert et al 2002b(Lienert et al , 2002c. Furthermore, negative correlations between fitness components and genetic variability were observed elsewhere (Oostermeijer et al 1995;Fischer and Matthies 1998;Fischer et al 2000), although this relationship may not be universal (Ouborg and van Treuren 1995;Lammi et al 1999).…”

“…Moreover, our study shows that the effects of habitat fragmentation are not uniform among species, but may depend on their life history. Since only two habitat-specific species are used, in conjunction with Swertia data (Lienert et al 2002b(Lienert et al , 2002c, generalization to include other species and habitat types is still difficult. It is unclear if the magnitude of the effects observed here indeed may threaten isolated or small populations in the long-term or if compensatory demographic effects may stabilize these populations.…”

GENÉTICA DA CONSERVAÇÃO DE Cabralea canjerana (Vell.) Mart. (Meliaceae) EM FRAGMENTOS FLORESTAIS DE MATA ATLÂNTICA NA APA FERNÃO DIAS

“…também estavam situados em regiões mais elevadas. No entanto, o que se percebe é um decaimento significativo da densidade populacional e da diversidade genética causada pela fragmentação de hábitats, tanto em espécies nativas (LIENERT et al, 2002;TOMIMATSU;OHARA, 2003;BACLES et al, 2006) quanto em espécies endêmicas (GONZALEZ-ASTORGA; NUNEZ-FARFAN, 2001;COLLEVATTI et al, 2001;DICK, 2001;SCHNEIDER et al, 2003).…”

“…Esse processo possui influência direta na composição genética de uma população, podendo alterar os padrões de dispersão de pólens e sementes (GHAZOUL, 2005) e, consequentemente, os padrões de distribuição da diversidade genética dentro e entre as populações de uma espécie. Uma população submetida a essas condições sofre ação de uma série de fatores genéticos e estocásticos, como a redução do tamanho populacional efetivo, aumento intrapopulacional da endogamia e da deriva genética que, em poucas gerações, pode causar redução drástica do valor adaptativo dos indivíduos, diminuindo suas resistências a doenças e a adaptações a novas mudanças ambientais, aumentando, assim, a suscetibilidade da população a uma extinção local (YOUNG et al, 2001;LIENERT et al, 2002;FAHRIG, 2003;AVISE, 2010;CABALLERO et al, 2010). Muitos estudos têm discutido o efeito negativo da fragmentação de hábitat sobre a diversidade genética de espécies arbóreas com respeito, particularmente, ao bioma Mata Atlântica (SALGUEIRO et al, 2004;CONTE et al, 2008;TARAZZI et al, 2009;RIBEIRO et al, 2009).…”