Pollen gene flow and molecular identification of full-sib families in small and isolated population fragments of Gleditsia triacanthos L.

Abstract

To analyze the utility of isolated remnant populations for full-sibling (full-sib) identification among open-pollinated single-tree progeny in the outcrossing and insect-pollinated tree Gleditsia triacanthos L. (honey locust), we performed paternity analyses in forest fragments from two geographic regions using nuclear microsatellites. The first plot (Butternut Valley population) comprised only 7 trees, and 552 seedlings from a single seed parent were characterized at nuclear microsatellites. A large number of putative pollen donors (59) were identified in kinship analyses, but their individual contributions to the progeny were highly variable. Kinship and paternity analyses identified 149 putative full-sibs for genetic mapping sired by an external (unsampled) pollen parent. To better assess the frequency of long-distance pollen dispersal, a total of 180 seeds were collected from 6 seed parents in another fragmented population. In both plots, contemporary pollen dispersal occurred generally from outside the plots (99.38% and 87.50%–100% at the Butternut Valley and Ames Plantation sites, respectively) and thus over very long distances (>12 000 m in the Ames Plantation) suggesting that in highly fragmented landscapes, insect pollinators of honey locust are likely very effective long-distance dispersers.