Search results for "Systematics"
showing 10 items of 6702 documents
Population-level consequences of risky dispersal
2014
Achieving sufficient connectivity between populations is essential for persistence, but costs of dispersal may select against individual traits or behaviours that, if present, would improve connectivity. Existing dispersal models tend to ignore the multitude of risks to individuals: while many assess the effect of mortality costs, there is also a risk of failing to find new habitat, especially when the entire inhabitable area remains both small and fragmented. There are few known rules governing whether individuals evolve to disperse more, or less, than what is ideal for population connectivity and persistence. Here we aim to fill this gap, while also noting that evolution might not only pr…
Mate recognition as a reproductive barrier in sexual and parthenogenetic Eucypris virens (Crustacea, Ostracoda)
2013
Mate selection is one of the motors of evolution and of particular importance in the case of organisms in which sexual and parthenogenetic populations coexist. Sexual populations of the ostracod species complex Eucypris virens are often mixed with parthenogenetic ones. A powerful mate selection mechanism must exist to avoid time, energy and sperm loss, for the maintenance and success of sexual reproduction in these mixed populations. There are four types of E. virens individuals: males (diploid), sexual females (diploid) and asexual females (parthenogenetic and either di- or triploid). From one parthenogenetic population and two populations with males of E. virens, we sampled early stage ju…
The significance of relatedness and gene flow on population genetic structure in the subsocial spider Eresus cinnaberinus (Araneae: Eresidae)
1998
Interdemic selection, inbreeding and highly structured populations have been invoked to explain the evolution of cooperative social behaviour in the otherwise solitary and cannibalistic spiders. The family Eresidae consists of species ranging from solitary and intermediate subsocial to species exhibiting fully cooperative social behaviour. In this study we, in a hierarchical analysis, investigated relatedness of putative family clusters, inbreeding and population genetic structure of the subsocial spider Eresus cinnaberinus. Five hierarchical levels of investigation ranging from large scale genetic structure (distances of 250 and 50 km level 1 and 2) over microgeographic structure (20 km 2 …
Stepping stones of life: natal dispersal in the group-living but noncooperative speckled warbler
2003
In most cooperatively breeding birds the offspring of one sex, usually male, delays dispersal to remain on the natal territory and helps its parents to rear subsequent young. Thus delayed dispersal could be the first step in the evolution of cooperative breeding. We studied natal dispersal in a population of the group-living speckled warbler, Chthonicola sagittata, based on observations of a colour-banded population over 3 years. Unlike other group-living members of the Acanthizinae, all juvenile males in this population dispersed to settle on foreign territories as subordinates, which do not help rear the young. Speckled warblers showed all the life history traits that are thought to resul…
The Horseshoe whip snake (Hemorrhois hippocrepis) on Ibiza: predator release in an invasive population
2020
Abstract The key to fighting a biological invasion may lie in understanding every variable that can explain its success. The Enemy Release Hypothesis (ERH) states that when an invader arrives to a new environment, the absence of its common enemies (predators, parasites and competitors) facilitates the invasion success. The Horseshoe whip snake (Hemorrhois hippocrepis) has been recently introduced from the Iberian Peninsula to the island of Ibiza, and it is currently threatening the only endemic vertebrate, the Ibiza wall lizard (Podarcis pityusensis). We hypothesized that the snake invasion success is caused by the absence of natural predators, and we checked the ERH by relating the tail br…
Foraging site fidelity shapes the spatial organisation of a population of female western barbastelle bats
2009
Abstract Information about the spatial distribution of individual foraging habitats, which determines the space required by a population to be viable, is vitally important for the conservation of bats. Detailed knowledge of this kind is crucial for the design of nature reserves and management plans. Recent field studies that examined habitat use and home range distribution of bats largely ignored factors like traditional range use vs. intra- and interspecific competition, which may be responsible for the spatial organisation of a population home range. We investigated the home range sizes and distribution of a maternity colony of the western barbastelle bat via radio telemetry in four conse…
Social overwintering and food distribution in the bank vole Clethrionomys glareolus
1991
We studied overwintering in the bank vole Clethrionomys glareolus in four 0.5 ha enclosures in an abandoned field in central Finland in the winter 1987/88. In two of the enclosures food was offered evenly distributed over the whole enclosed area (Even Enclosures = EE), in the two others food was offered in one feeding patch with four feeding chambers 2 m apart (Patchy Enclosures = PE). Food was provided in about the same amount in both enclosures. The experiment commenced in early October, with 13 females and 11 males in EEs and 12 + 13 voles in PEs. After two months the voles in the PEs were concentrated around the feeding patches. Territoriality was not observed in EEs, instead the voles …
Sources of variation in survival and breeding site fidelity in three species of European ducks
2002
Summary 1 We used long-term capture–recapture–recovery data and a modelling approach developed by Burnham (1993) to test a priori predictions about sources of variation in annual survival rates and fidelity within a population of individually marked females in three species of European ducks from a breeding ground study site in Latvia. 2 True annual survival was higher for diving ducks (tufted duck 0·72, common pochard 0·65) and lower for northern shoveler (0·52). Survival of female diving ducks was positively correlated with mean winter temperatures at Western European wintering areas, the relationship being much stronger for pochard. 3 We present the first unbiased estimates of breedin…
Ecological genetics of a cyclical parthenogen in temporary habitats
1995
Populations of the rotifer Brachionus plicatilis inhabiting three temporary ponds in Torreblanca Marsh (Castellon, Spain) were regularly screened for allozyme variation, sexual reproduction levels and population densities during an annual cycle. Relevant ecological parameters in the ponds were also recorded. The electrophoretic survey of the three ponds (Poza Sur, Poza Norte and Canal Central) revealed a high level of overall genetic polymorphism in four marker loci, but only 13 multilocus genotypes were found. We classified clones into three clonal groups (SS, SM, L) characterized by unique arrays of alleles in the four marker loci, and significant differences in body shape and size. Clona…
Long-term decrease in sex-specific natural mortality of European lobster within a marine protected area
2013
Marine protected areas (MPAs) and marine reserves hold promise as tools for nature conservation and fisheries management, but data on long-term demographic effects are still sparse. Here, we use a unique capture-mark-recapture data set from Kavra, an MPA on the west coast of Sweden where fishing for European lobster Homarus gammarus has been banned since 1989, to directly quantify annual survival probabilities in the absence of harvest mortality. The non-migratory behaviour of this species allowed multiple recaptures and releases of a large num- ber of individuals within the MPA. We found strong evidence for a long-term decrease in sex - specific natural mortality throughout the study perio…