Geometrical Factors and Metapopulation Dynamics of the Bush Cricket, Metrioptera bicolor Philippi (Orthoptera: Tettigoniidae)

Abstract

This paper presents a metapopulation study of the bush cricket, Metrioptera bicolor, living in a recently fragmented landscape. The species inhabits grass and heathland patches of varying area and isolation. Analyses are made of how these geometrical factors affect local population size and density, distribution pattern, and the probability of local extinction and colonization. The proportion of available patches occupied varied between 72 and 79% during 1985–1990. Unoccupied patches were smaller and more isolated than those that were occupied. Patches where populations became extinct during this period were smaller than those with persisting populations. Since local population size was well correlated with patch area, it was clear that stochastic extinctions only occurred in small populations. Critical patch size for population extinction was approximately half a hectare. Colonized patches were less isolated than those that had not been colonized. Critical inter‐patch distance for colonization was about 100 meters. The turnover was restricted to an identifiable share of the available patches. Only 33% of the patches were so small that extinction due to stochastic causes could be considered highly probable. This metapopulation will therefore most likely persist over a considerable period in its present spatial structure. There are apparent threats of further fragmentation, however, and nothing is known about the likelihood of large‐scale extinctions resulting from extremely unfavorable weather conditions. Nevertheless, our results show that it is appropriate to include geometrical factors in metapopulation models.

Local and regional dynamics of a specialist herbivore: overexploitation of a patchily distributed host plant

“…Kindvall and Ahlén 1992;Kruess and Tscharntke 1999). My investigations, however, deal with a monophagous weevil species that has probably evolved in a highly fragmented habitat and is now confronted with increasing connectivity due to K.…”

Dinámica metapoblacional, ocupación espacial y migración en bivalvos de importancia comercial: el caso de la almeja Tawera gayi (Bivalvia: Veneridae) en el Mar Interior de Chiloé

“…Al agregar otros factores que acrecienta aún más la disminución del tamaño del hábitat, es esperable que las poblaciones difícilmente logren una conectividad, ya que un hábitat pequeño mantiene poblaciones reducidas (Kindvall & Ahlen, 1992;Kindvall, 1996). Por ejemplo, es conocido el rol que tiene la textura de los sedimentos en el éxito de la colonización de bivalvos de fondos sedimentarios (Urban, 1994), restringiendo las estrategias de expansión y sobrevivencia de la metapoblación.…”

Metapopulation Structure and Movement of a Threatened Butterfly Parnassius bremeri (Lepidoptera: Papilionidae) in Korea

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