New Zealand Journal of Botany abstract

Inbreeding depression in the gynodioecious shrub Hebe subalpina (Scrophulariaceae)

LYNDA F. DELPH*

Department of Biology
Indiana University
Bloomington
Indiana 47405, USA

DAVID G. LLOYD

Department of Plant and Microbial Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
* Author for correspondence

Abstract  Inbreeding depression caused by self-fertilisation was examined in the gynodioecious shrub Hebe subalpina under two planting regimens, non-competitive and competitive. We found differences among families in the magnitude of inbreeding depression, ranging from 0.31 to 0.63. On average, outcrossed progeny grew nearly twice as large as selfed progeny, and the coefficients of variation (CVs) for dry mass were lower for outcrossed progeny than selfed progeny within the non-competitive regimen. Planting regime had a highly significant effect on dry mass, such that plants grown in the competitive regimen were an order of magnitude smaller than those in the non-competitive regimen, and they also had higher CVs. However, planting regimen did not significantly affect the magnitude of inbreeding depression. Our results suggest that intrinsic differences exist in the growth rate of selfed and outcrossed individuals, and that inbreeding depression helps to maintain females at a high frequency in the population. We suggest that among-family variation in the magnitude of inbreeding depression is likely in gynodioecious species because of differences in inbreeding caused by gender.

Keywords  gynodioecious; Hebe subalpina; inbreeding depression; male-sterility

B95026

Received 23 June 1995; accepted 16 November 1995

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