Evidence for local outbreeding depression in the Mediterranean island endemic Anchusa crispa Viv. (Boraginaceae)

In this study we examined the relative effects of inbreeding and outbreedin g on offspring fitness over two generations in Anchusa crispa Viv., a rare species which on Corsica (France) occurs in small populations composed of p atches of few individuals. Self- and outcross-pollinations were carried out in a single population and F-1 progeny grown to flowering. Plants grown fr om selfing and outcrossing were then selfed or outcrossed to produce F-2 in dividuals in four combinations of pollination treatments over two generatio ns, i.e. self + self, self + outcross, outcross + self and outcross + outcr oss. In the F-1 generation, selfed progeny had a significantly greater numb er of cymes per plant than outcrossed progeny (P = 0.006). Plants from two generations of selfing had fewer seeds per fruit (P = 0.06) but a significa ntly greater survival rate (P < 0.001) and a greater number of cymes (P = 0 .06) than those from two generations of outcrossing. Selfed F-2 from outcro ssed F-1 had a significantly greater number of cymes (P < 0.01) than outcro ssed F-2 from outcrossed F-1. In the comparison between selfed and outcross ed F-2 from selfed F-1 the former had a significantly greater survival rate (P < 0.001), but the latter significantly more flowers per cyme (P < 0.05) . Together, these results indicate that outbreeding depression may occur on a very local scale within populations of this rare endemic species, with i mportant implications for the conservation of rare plants.