24 research outputs found
Scaling up the effects of inbreeding depression from individuals to metapopulations
Abstract Inbreeding is common in nature, and many laboratory studies have documented that inbreeding depression can reduce the fitness of individuals. Demonstrating the consequences of inbreeding depression on the growth and persistence of populations is more challenging because populations are often regulated by density- or frequency-dependent selection and influenced by demographic and environmental stochasticity. A few empirical studies have shown that inbreeding depression can increase extinction risk of local populations. The importance of inbreeding depression at the metapopulation level has been conjectured based on population-level studies but has not been evaluated. We quantified the impact of inbreeding depression affecting the fitness of individuals on metapopulation persistence in heterogeneous habitat networks of different sizes and habitat configuration in a context of natural butterfly metapopulations. We developed a spatial individual-based simulation model of metapopulations with explicit genetics. We used Approximate Bayesian Computation to fit the model to extensive demographic, genetic, and life-history data available for the well-studied Glanville fritillary butterfly (Melitaea cinxia) metapopulations in the Ć
land islands in SW Finland. We compared 18 semi-independent habitat networks differing in size and fragmentation. The results show that inbreeding is more frequent in small habitat networks, and consequently, inbreeding depression elevates extinction risks in small metapopulations. Metapopulation persistence and neutral genetic diversity maintained in the metapopulations increase with the total habitat amount in and mean patch size of habitat networks. Dispersal and mating behavior interact with landscape structure to determine how likely it is to encounter kin while looking for mates. Inbreeding depression can decrease the viability of small metapopulations even when they are strongly influenced by stochastic extinction-colonization dynamics and density-dependent selection. The findings from this study support that genetic factors, in addition to demographic factors, can contribute to extinctions of small local populations and also of metapopulations. This article is protected by copyright. All rights reserved.Peer reviewe
Causes of hatching failure in endangered birds
About 10 per cent of birdsā eggs fail to hatch, but
the incidence of failure can be much higher in
endangered species.Most studies fail to distinguish
between infertility (due to a lack of sperm) and
embryo mortality as the cause of hatching failure,
yet doing so is crucial in order to understand the
underlying problem. Using newly validated techniques
to visualize sperm and embryonic tissue,
we assessed the fertility status of unhatched eggs
of five endangered species, including both wild
and captive birds. All eggs were classified as āinfertileā
when collected, but most were actually fertile
with numerous sperm on the ovum. Eggs of captive
birds had fewer sperm and were more likely
to be infertile than those of wild birds. Our findings
raise important questions regarding the
management of captive breeding programmes