Striped mouse

Striped mouse

Striped mouse (Rhabdomys pumilio) on the cover of the August edition of Behaviour

Striped mouse (Rhabdomys pumilio) on the cover of the August edition of Behaviour
My photo and the accompanying paper (see List of publications) were published in this issue.

Friday, April 11, 2014

Summary: Dynesius & Jansson (2000)

Over the course of Earth's history, climates have varied widely. Some climate cycles are reported on the scale of 10-100 thousand years, such as Milankovitch oscillation. Milankovitch cycles have been demonstrated to influence the location and size of species geographical distributions. Dynesius & Jansson (2000) further suggest that Milankovitch cycles also drive geographical patterns of species diversity, polyploidy, degree of specializations and the dispersal ability of organisms. When species ranges  are influenced by these climate cycles, they can be termed ORDs, or "orbitally forced species' range dynamics". These ORDs may constrain short-term evolutionary processes. Although adaptations may accumulate between climatic shifts, they may be lost when the climate shifts, due to population extinction of variation in selection pressure. The size of ORDs varies on both temporal and spatial scales, and can function to decrease gradual speciation, increase species range size and proportion of polyploid species. ORDs favour dispersability and tend to favour generalizations. Dynesius & Jansson (2000) indicate that large ORDs can promote species persistence (neither extinction nor speciation) and that ORDs show a corresponding increase with latitude (although how these ORDs vary with longitude or altitude is not indicated). One of the latitudinal patterns observed by ORDs is Rapoport's rule - a gradient in species' range sizes and diversity. Dynesius & Jansson (2000) argue that ORDs of different strengths may explain several biological phenomena (i.e. one driving force as opposed to many). ORDs provide a new opportunity for developing conservation strategies on different environmental scales.

Thursday, April 3, 2014

Summary: Dukas & Jongsma (2012)

Female mate choice is common in the animal kingdom and females and males may come into conflict over a female's choosiness. In particular, males that are chosen less frequently by females may resort to forceful copulations in order to gain some reproductive fitness. In fruit flies Drosophila melanogaster, males may force-copulate with sexually immature females just after eclosion, a particularly vulnerable time for females. Although males only achieve approximately 20% of successful matings this way, the results for females are significant. Females suffer reduced longevity, high wing damage and show lowered reproductive success (through generation of fewer progeny, which they can still produce). Although females are capable of remating at sexual maturity after a forced copulation, mating is generally followed by a period of diminished receptivity and attractiveness, meaning that females may not be able to mate until a later time. Dukas & Jongsma (2012) quantified the effects of forced vs. consensual matings on the receptivity and attractiveness of females, to determine whether forcibly mated females are able to overcome the effects of mating by showing faster return to receptivity and attractiveness. Although forcibly mated females appeared as attractive as same-age virgins, and were more attractive than recently consensually mated females, Dukas & Jongsma (2012) found that they remated at a lower frequency than same-age virgins, but a higher frequency than recently mated females. In the case of fruit flies, it seems that males benefit through forced copulations by gaining some fitness benefits through generation of progeny. Although damaging to females, females are able to overcome this negative behaviour, and can gain matings later through return to attractiveness and receptivity (even if only partially).