LIMITED DISPERSAL AND PROXIMITY‐DEPENDENT MATING SUCCESS IN THE COLONIAL ASCIDIAN BOTRYLLUS SCHLOSSERI

Abstract

Abstract. -Although the propagules of many sessile organisms have the capacity to disperse over large distances, dispersal is often spatially restricted. In this paper, I document, using a combination of mark/recapture techniques and histocompatibility assays, dispersal distance of the planktonic larvae of the sessile, colonial sea squirt Botryllus schlosseri. Both of these methods indicate that most larvae remain within a meter of their birthplace. Such limited dispersal should lead to increased matings among relatives, and the potential for inbreeding depression. However, the success of: 1) fertilization, 2) embryogenesis, and 3) larval metamorphosis all decrease as distance between mated colonies increases. The spatial scale over which this decrease in mating success occurs is concordant with the estimates of dispersal distance based on the larval mark/recapture data and histocompatibility assays. Taken together, these results imply that inbreeding depression is not a necessary consequence of limited dispersal and consanguineous matings in B. schlosseri.

The association of coloniality with parental care of embryos

“…Distances traveled by sperm of a colonial stolidobranch ascidian can exceed distances traveled by larvae (Grosberg, 1987(Grosberg, , 1991Yund, Murdock, & Johnson, 2007).…”

Somatic and germ cell parasitism in a colonial ascidian: Possible role for a highly polymorphic allorecognition system

“…The importance of G͞SCP as a selective factor may be quite dramatic in some populations. The rate of chimerism within natural populations of B. schlosseri can reach levels as high as 20% (9,26) and our data suggest a 40% incidence of G͞SCP within those chimeras. Finally, as predicted by Buss's hypothesis (1), we showed that the rate of G͞SCP drops considerably when colony rejection occurs instead of fusion.…”

Sexual Plasticity and Self-Fertilization in the Sea Anemone Aiptasia diaphana

“…In marine species that reproduce by broadcast spawning (i.e., shedding of male and female gametes into the water column) and that rely on water currents and movement of sperm between individuals, the rapid dilution and relatively short lifespan of sperm means that outcrossed fertilization is proximity- dependent [31]. In sessile organisms in which the only proximate partner is a clone- mate, self-fertilization becomes the only method of achieving meiotically-driven genetic variability.…”