Effect of Propagule Size and Landscape Structure on Morphological Differentiation and Asymmetry in Experimentally Introduced Roesel's Bush‐Crickets
Abstract: Conservation efforts involving introductions, reintroductions, and translocations of populations have an inherent and inescapable problem of small initial populations. Small founding populations are likely to have a small proportion of the genetic variability carried by the original population. This may manifest phenotypically through changes in individual morphology, such as decreased body size, increased degree of fluctuating asymmetry, or changing susceptibility to environmental stressors. I investigated the effects of population and landscape variables on the morphology and fluctuating asymmetry in individual bush‐crickets by examining 584 individual Roesel's bush‐crickets (Metrioptera roeseli) from 29 established populations from different propagule sizes that were introduced in areas previously unoccupied by the species. The introduction sites were in landscapes similar to where the species occurs naturally, but sites differed in connectivity and amount of surrounding suitable habitat. Individuals were caught up to 9 years after the initial introduction, and five different morphological traits were measured. All introduced individuals originated from the same population and individuals from this source population were also collected for comparison in the analyses. Male body weight and female body length were positively affected by initial population size and degree of connectivity of the introduction patch. Isolation also affected fluctuating asymmetry in male tibias, with a higher degree of asymmetry in males that came from more isolated populations. In a relatively short time period, I was able to detect the effect of isolation and small population sizes on morphology and asymmetry. Small propagule sizes and habitat isolation are both likely to have resulted in decreased genetic diversity, the latter by reducing population sizes through decreased survival. These results show the importance of both large propagule sizes and good connectivity of habitats when introducing populations. The differences between the sexes in response to the variables examined also indicate that studies on morphology and fluctuating asymmetry need to consider males and females separately to avoid inaccurate generalizations of the state of the population.
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Document Type: Research Article
Affiliations: Department of Conservation Biology, P.O. Box 7002, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden
Publication date: August 1, 2005