Variation in life-cycle between three rare and endangered floodplain violets in two regions: implications for population viability and conservation

Abstract

Abstract:We studied the demography of Viola elatior, V. pumila, and V. stagnina, three rare and endangered Central European floodplain species, to (i) analyse variation in life-cycles among congeners and between regions (Dyje-Morava floodplains, Czech Republic; Upper Rhine, Germany), (ii) to define sensitive stages in the life-cycles, and (iii) to identify possible threats for population viability and species conservation. Matrix models were based on the fate of marked individuals from a total of 27 populations over two years. We analysed population growth rate (λ), stage distribution, net reproductive rate (R0), generation time, age at first reproduction, and elasticity and calculated a life table response experiment (LTRE). Most populations were declining and λ did not differ between species or regions during the observed interval. Despite higher probabilities for survival and flowering in the Dyje populations, R0 was higher in the Rhine populations. Also other demographic traits showed consistent differences between regions and/or species. Complex life-cycles and large variation in λ precluded unequivocal identification of sensitive stages or vital rates for conservation. Variation between regions may be a consequence of differences in habitat quality. Our results suggest that deterministic processes such as reduced management, succession, habitat destruction, and lack of disturbance through reduced or eliminated flooding present the strongest threat for the viability and persistence of populations of the three floodplain violets as compared with stochastic processes. However, the persistent seed bank of the species may buffer populations against environmental variation and represents a reservoir for recovery after resumption of suitable land-use management.

Using genomic information for management planning of an endangered perennial, Viola uliginosa

“…Based on the principal component analysis, the observed data were located among the data simulated according to scenario 2 and distant from data simulated according to scenario 1 (see Figure ). Divergence times were given in generations, and as there were no estimates for a generation time in V. uliginosa , we used a mean of estimates obtained from V. elatior , V. pumila, and V. stagnina from Eckstein, Danihelka, and Otte (), 9.44 years, to transfer the generations into years (Table ). Using this estimate, divergence from the common ancestor occurred 9,140 years BP (95% CI: 4,630–9,360; 824 generations), divergence of Estonian populations 550 years BP (95% CI: 280–1,650; 85.1 generations), and divergence of Finnish populations just 100 years BP (95% CI: 94.4–140; 11.6 generations).…”

Region versus site variation in the population dynamics of three short‐lived perennials

“…Analysing life‐history differences between and within regions is rarely done (but see Menges & Dolan 1998; Angert 2006; Hyatt & Araki 2006; Eckstein, Danihelka & Otte 2009; Maron, Crone & Horvitz 2010), although such studies add an important dimension to our understanding of variation in population dynamics. In our case, nested LTREs revealed large regional differences in life histories within species, even though life‐history differences were also large among sites within regions (Fig.…”

“…However, little is known about demographic variation across regions, such as different countries or states that may lie in different climate zones. For example, 41 out of 80 studies on perennial plants considered only one site (Salguero‐Gomez & Casper 2010), while only three studies analysed population dynamics in more than one site in different regions (Menges & Dolan 1998; Hyatt & Araki 2006; Eckstein, Danihelka & Otte 2009). Menges & Dolan (1998) found significant differences in the growth rates of Silene regia populations among regions within their mid‐western distribution and suspected them to be related to regional differences in frequency of summer droughts.…”

“…In addition, a number of studies have shown that populations may buffer variation among sites or years (Yamada et al. 2007; Eckstein, Danihelka & Otte 2009; Davison et al. 2010; Horvitz, Ehrlén & Matlaga 2010; Salguero‐Gómez & Casper 2010) by negative co‐variances among vital rates, indicating that some vital rates are above average in some years or sites and other vital rates relatively high in other years or sites.…”

Population structure and genetic diversity of relict populations of Alyssum montanum on limestone cliffs in the Northern Swiss Jura mountains

“…The majority of the populations investigated (9 out of 12) exhibits a so-called ''invasive population structure'' which is characterized by a high proportion of seedlings and small plants in relation to large plants (Oostermeijer et al 1994). This particular type of population size structure most frequently occurs in early successional stages of different habitats (Oostermeijer et al 1994;Brys et al 2004;Eckstein et al 2009). The cliff vegetation is disturbed by storms and/ or rock climbing and resting hikers on the top of the cliffs.…”