Individual and population level determinants of immigration success on local habitat patches: an experimental approach

Abstract

The effect of population density on immigration success of young root voles was studied in a factorial experiment where immigrants of three different types were translocated from donor populations to recipient habitat patches with experimentally manipulated population sizes. The different types of immigrants were: (1) residents, animals that had remained in their natal patch; (2) colonists, animals that already had successfully dispersed and settled in a new patch; and (3) transients, animals roaming around in a non‐habitable matrix area of the donor population. Generally, we found evidence for a negative density‐dependent immigration success in terms of survival, rate of sexual maturation and body growth rate. With respect to the survival rate, the degree of density dependence differed among the three immigrant types. Our findings are discussed with respect to the degree of rescue effect immigrants may have on a recipient population depending on population density, and also its relevance concerning translocation of individuals for conserving endangered populations.

Geographical variation in wolf spider dispersal behaviour is related to landscape structure

“…Since we did not record any bias in sex ratio within populations (D. Bonte, unpublished data), this mode of condition-dependent dispersal is, however, unlikely (Ims 1990). Condition-dependent dispersal, in contrast to selection-based dispersal, is believed to be expressed at the individual level, that is, within populations (Gundersen et al 2002). Because our patterns of dispersal could not be related to individual condition (i.e.…”

“…An alternative possibility for condition-dependent dispersal, however, is that spiderlings originating from large populations (i.e. goodcondition ones) show a higher dispersal tendency, since immigration into new competitive environments requires energetic reserves (Gundersen et al 2002). In this way, condition per se is a possible trigger for higher dispersal in spiders originating from large, continuous landscapes.…”

Human-caused mortality influences spatial population dynamics: Pumas in landscapes with varying mortality risks

“…However, after accounting for this mortality, the effects of heavy harvest remained influential, indicating direct mortality did not mediate the effects of harvest. High population turnover from human-caused mortality likely indirectly reduced dispersal distances by opening territories, encouraging settlement near dispersers' natal range (Gundersen et al, 2002;Smith, 1993;Stoner et al, 2006;Wielgus et al, 2001). …”

Effects of Female Immigrants on Demography and Social Organization of Prairie Vole (Microtus Ochrogaster) Populations

“…Inversely density-dependent immigration rates have been observed in previous studies (Gundersen et al 2002;Lin and Batzli 2001). Territorial females, particularly at high densities, can form a social fence that impedes immigration (Hestbeck 1982).…”