| Unionid freshwater mussels are a highly imperiled group. Little is known about their dispersal, which is a complex process that depends on the transport of larvae (glochidia) and juveniles in the water column, and movement of their host fish during the mussels' parasitic stage. The hypothesis of this research was that specialization with respect to host infection strategy influences dispersal abilities. This was examined by comparing dispersal processes and early life history traits among Lampsilini mussels. I focused on Actinonaias ligamentina that broadcasts its glochidia and was therefore considered a "generalist", and Epioblasma triquetra, a "specialist" that captures its host between the valves. Release experiments with stained glochidia showed that glochidia of the generalist can travel in the water column considerable distances (up to 100 m in low flow conditions), whereas glochidia of the specialist can attach directly to the trapped fish. Transport distances of juvenile mussels of both species may extend over 10s of m as suggested by a combination of field and lab experiments, if turbulent flow conditions diminish the effect of lower release heights in the water column from the specialist's benthic hosts. Examination of host fish movements were based on a mark-recapture study and a literature review, which indicated that the specialist's host fish has significantly shorter movement distances (10s of m) than host fish of the generalist (100s of m to km).;In addition, the conservation statuses of mussels in Ontario appear to be associated with the movement distances of their host fish. Overall, the generalist (broadcaster) has . considerably larger dispersal distances than the specialist (host capture), which is reflected in the findings that early life history traits relevant for dispersal differ considerably between broadcasting and host capture species. Other species that attract hosts with mimetic mantle flaps and packages of glochidia (conglutinates) fill positions between these extremes with respect to both dispersal abilities and early life history traits. This study demonstrates that dispersal distances can differ considerably among mussel species, but are predictable based on their ecology, which is a crucial first step to understand connectivity of populations and to develop sound conservation strategies. |
