Crossing experiment and mating trial data for New Zealand Dolomedes undergoing introgression

Introgression is a highly influential process in evolution, where genes
flow between species that are not fully reproductively isolated. Studies
on introgression often focus on describing gene transfer and environmental
changes that facilitate the meeting of species. However, the impact of
mating systems and behaviour that facilitate gene transfer is less
well-known. Dolomedes aquaticus and D. minor are sister species of fishing
spiders undergoing one-way, geographically limited mitochondrial
introgression, making them an excellent case study for the factors that
promote and limit introgression. We used a combination of field
observations and crossing experiments to systematically investigate
potential pre-fertilisation barriers that could limit introgression and
explain the one-way and geographic barriers to introgression in these
species. We found that habitat overlap and timing of reproductive maturity
were not likely to be important limiting factors to introgression.
However, behaviour was an important factor, with male mate choice being
implicated in the geographic limitation, and female mate choice being
implicated in the one-way limitation. Our results show the importance of
using behavioural approaches in the investigation of introgression.