Animals don’t move across landscapes at random, and the way in which they disperse has important implications for the dynamics of populations in fragmented habitat. There are a number of ways in which we can use genetic data to improve our understanding of dispersal in fragmented ecosystems.
Sam Banks and David Lindenmayer used genetic tagging and parentage analyses to identify the natal locations and dispersal destinations of the agile antechinus (Antechinus agilis). They used this information to understand the individual and environmental factors that influenced the observed dispersal choices by these native marsupial carnivores in a fragmented landscape near Tumut, NSW.
Female antechinus barely moved at all from where they were born, but males moved an average of over 1 km, with some moving nearly 8 km from their natal site. Not bad for an animal that fits in the palm of your hand! Males were more likely to disperse out of their natal patch if it was not geographically isolated from other patches, and if they were highly related to the females in their home patch (to avoid inbreeding). Surprisingly, inbreeding avoidance also influenced their choice of dispersal destination, in that they were most likely to settle in patches containing females to whom they were highly unrelated. They also preferred to disperse to patches containing lots of females, good quality habitat, and those that were linked to their natal patch by corridors of eucalypt forest.
These findings highlight the importance of individual-level dispersal data for understanding how multiple processes drive dispersal in modified landscapes. The detailed individual-level data improved our understanding of the major environmental drivers of dispersal choices and identified novel genetic and behavioural processes shaping non-randomness in individual dispersal patterns.
The research also uncovered new genetic patterns by showing that the genetic context in which individuals make dispersal choices is likely to differ between fragmented and unfragmented habitat. The researchers showed that the spatial scale of genetic neighbourhoods can be large in fragmented habitat, such that dispersing males can potentially settle in the presence of genetically similar females after moving considerable distances, thereby necessitating both a choice to emigrate and a choice of where to settle to avoid inbreeding.
Banks SC and DB Lindenmayer (2014) Inbreeding avoidance, patch isolation and matrix permeability influence dispersal and settlement choices by male agile antechinus in a fragmented landscape. Journal of Animal Ecology 83: 515-524.