Hierarchical genetic structure and effective population sizes in Phalacrus substriatus

Abstract

In this paper we present an analysis of the hierarchical population structure of the mycophagous beetle Phalacrus substriatus. The analysis showed that P substriatus is substructured at both hierarchical levels studied, among islands and among local populations within islands. The level of differentiation among local populations was about three times as high as among different islands (FPL = 0.043 and FLT = 0.013, respectively). This stands in marked contrast to the patterns expected, based on the dispersal of 1? substriatus, as the average dispersal distance of individual beetles is less than a metre per generation. Several explanations are discussed which can explain the observed patterns. We also estimated the effective population size for both hierarchical levels. The results show that the NIN ratios are well below unity, both for local populations and for islands. The average Ne/N ratio for local populations was only 0.210 (geometric mean, 0.172), whereas for islands the observed Ne/N ratios ranged from 0.75 to 0.98. Population subdivision is expected to increase the global (island) effective population size under equilibrium situations. However, random extinctions and recolonizations can lead to significant reductions in the global effective population size. Because population turnover is a commonly occurring phenomenon in P substriatus, we argue that this is, at least partly, responsible for the low Ne/N ratios observed in this species. The low effective population sizes, both for local populations and for islands, will result in rapid erosion of a large proportion of the genetic variation present. The present study thus highlights the need to take random processes, such as extinction-recolonization dynamics, into account when studying effects of spatial subdivision.

Effective population sizes and migration rates in fragmented populations of an endangered insect (Coenagrion mercuriale: Odonata)

“…Principally following Frankham's (1995) review there has been substantial interest in quantifying the range of N e / N across taxa and under different demographic and environmental conditions. In C. mercuriale , this ratio varies from 0·006 to 0·4 that is lower than most values reported by Frankham (1995) for insects (17 studies), except the seaweed fly Coelopa frigida ( N e / N = 0·0047 and 0·0009); subsequent estimates of N e / N in insect populations varied between 0·098 and 0·491 (mean = 0·21) for a beetle (Ingvarsson & Olsson 1997). Thus, there are still too few data to evaluate whether certain insect taxa or life histories have characteristic N e / N ratios.…”

The annual number of breeding adults and the effective population size of syntopic newts (Triturus cristatus, T. marmoratus)

“…For discussions of further possible violations of assumptions of the temporal method see: Waples (1989a); Husband & Barrett (1992); Scribner et al . (1997); Ingvarsson & Olsson (1997); Miller & Kapuscinski (1997); and Lehmann et al . (1998).…”

Intra-Population Genetic Structure of Oryza rufipogon Griff. in Yunnan, China

“…Although intra-population genetic structure has been received far less attention than inter-population, there is some evidence to suggest that genes and genotypes are not distributed at random within populations (Christiansen and Feldman 1975, Turner et a/. 1982, Loveless and Hamrick 1984, Epperson 1989, Chesser 1991, Huang 1994, Husband and Barrett 1995, Johannesen and Loeschcke 1996, Invarsson and Olsson 1997, Giles et a/. 1998, Owuor et a/.…”