Metapopulation dynamics and viability of the bog fritillary butterfly Proclossiana eunomia
(2003)
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- Abstract
- Nowadays, the Earth is facing an unprecedented biodiversity crisis, notably because of habitat loss, deteioration and fragementation. Understanding the consequences of habitat fragmentation is therefor of prime importance for conversation biologists; the metapopulation concept is especially helpful in that. The present thesis focuses on metapopulation dynamics and variability of a threatened butterfly species in Western Europe, the bog fritillary Proclossiana eunomia. Several patch systems located in two major areas were used in this study, differing in their fragmentation level concerning habitats of the bog fritillary: (1) the Plateau des Tailles (southern Belgium) as a highly (Lienne Valley) or moderately (Pisserotte) fragmented landscape and (2) the Kuhmo area (central Finland) as a nearly continuous system. After having stated the context and state-of-the-art of the basic concepts I use (notably, conversation biology, metapopulation and population viability analysis), I first focus on local dynamics (mainly demography but also between-path correlation). From 11 Capture-Mark-Recapture (CMR) data sets, each corresponding to one adult generation of P. eunomia in the Lienne Valley metapopulation, I used Constrained Linear Models (CLM) -of which a thorough description is given with tricks for effective use, as well as a comparison with the Jolly-Seber method- to estimate the mean and the variance of individual parameters (survival and catchability) and population features (population size, sex-ratio and recruitment rate) at the scale of the whole population, as well as their sources of variations. Highly conserved patterns of daily variation are seen for demographic parameters; they are related to life history traits of P. eunomia. Density-dependent growth, modulated by climatic conditions is shown from the series of population sizes. As a complement to adult demagraphy, female fecundity and larval survival have been estimated by a specific experiment. Then I compare metapopulation functioning between a highly fragmented landscape (Lienne Valley) and a nearly continuous one (Kuhmo). Demography seems relatively unaffected by fragmentation while effect on dispersal are far far from negligible, with a drop in dispersal rate in the fragmented landscape. I then turn to a comparison between two landscapes (on the same Belgian upland, but one highly fragmented with low quality matrix, Lienne Valley, and an other more aggregated with high quality matrix, (Pisserotte) of the female dispersal behaviour (assessed by tracking individuals). It reveals a U-turn behaviour at habitat patch boundary far higher in the highly fragmented landscape, a relationship absent in the aggregated sustem with high boundary permeability. These results (already observed in the previous comparison : Lienne Valley vs. Kuhmo) fit the observed emigration patterns in both systems. Finally, results about demography, density dependence, environmental stochasticity, between-patch dispersal and correlation of local dynamics are used to build (using RAMAS-GIS as platform) a structured metapopulation viability analysis for the highly fragmentd Belgian metapopulation of P. eunomia (Lienne Valley). Sensitivity analysis shows a higher effect of demographic parameters than of dispersal ones, not unexpected in a metapopulation with a few and highly dissimilar populations. COmparison among scenarios highlights the potencial danger represented by the current management pratice with rustic cows as well as the one of climate change on this glacial relict species. To conclude, besides summarizing the major insights gained on metapopulation functioning of the bog fritillary, for itself and its protection but also as a model species, I discuss the potentiality of generalising some conclusions or parameter estimates to closely related species. As it will never be possible to gather so many data on every endangered species, such generalisations seem of prime importance in the process of protecting most of Earth's species, from extinction, notably with the help of population viability analysis.
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Citations
Schtickzelle, N. (2003). Metapopulation dynamics and viability of the bog fritillary butterfly Proclossiana eunomia. https://hdl.handle.net/2078.5/124227