Catastrophic Floods May Pave the Way for Increased Genetic Diversity in Endemic Artesian Spring Snail Populations

The role of disturbance in the promotion of biological heterogeneity is widely recognised and occurs at a variety of ecological and evolutionary scales. However, within species, the impact of disturbances that decimate populations are neither predicted nor known to result in conditions that promote genetic diversity. Directly examining the population genetic consequences of catastrophic disturbances however, is rarely possible, as it requires both longitudinal genetic data sets and serendipitous timing. Our long-term study of the endemic aquatic invertebrates of the artesian spring ecosystem of arid central Australia has presented such an opportunity. Here we show a catastrophic flood event, which caused a near total population crash in an aquatic snail species (Fonscochlea accepta) endemic to this ecosystem, may have led to enhanced levels of within species genetic diversity. Analyses of individuals sampled and genotyped from the same springs sampled both pre (1988–1990) and post (1995, 2002–2006) a devastating flood event in 1992, revealed significantly higher allelic richness, reduced temporal population structuring and greater effective population sizes in nearly all post flood populations. Our results suggest that the response of individual species to disturbance and severe population bottlenecks is likely to be highly idiosyncratic and may depend on both their ecology (whether they are resilient or resistant to disturbance) and the stability of the environmental conditions (i.e. frequency and intensity of disturbances) in which they have evolved

Mating behaviour by the haddock (Melanogrammus aeglefinus)

This study examines the full repertoire of haddock reproductive behaviour, monitored in an aquarium for 3 months over each of two successive spawning seasons. Observations showed that male haddock were territorial and that visits to their territories by females triggered courtship behaviour, leading to spawning. Entry of females to the territories was induced by an acoustic and visual self-advertisement of displaying males, termed patrolling behaviour, exhibited for many hours each night for several months. The existence of sneaking behaviour by non-territorial males was observed for the first time for haddock and was supported by genetic data. Overall our observations are consistent with the behaviour expected from lekking species, as in the cod, a closely related species. Lekking is said to occur when non-resource-based aggregations of males are visited by females for the purpose of mating. Implications for the management of fish stocks are discussed