Enterolobium

Abstract: Costa Rican horses ranging free in deciduous forest-grassland habitats swallow about half of the seeds in the Enterolobium cyclocarpum fruits that they eat, and six such horses defecated at least 9-56% of the seeds alive. While about three-quarters of the surviving seeds appeared by the 14th d after ingestion, about a quarter of the surviving seeds emerged 15-60 d after ingestion. The horse kills Enterolobium seeds by digestive processes shortly after the seed germinates in response to the moisture of the intestinal tract. More than 90% of the seeds that survived the trip did so as hard dormant seeds. They showed no indication that they would germinate more rapidly (break dormancy more rapidly) than seeds planted directly from the fruits. The horse-seed interaction sug- gests that Pleistocene horses may have contributed to both local and long-distance population re- cruitment by Enterolobium cyclocarpum, and contemporary horses certainly have the potential to do so.

Abstract: We compared the rate of pollen deposition, the likelihood of fruit production, the number of seeds per fruit, the outcrossing rate, and the progeny vigor of the tropical dry forest tree Enterolobium cyclocarpum for individuals in pastures vs. individuals in continuous forest. We found that flowers from trees growing in continuous forests were more likely to have pollen deposited on their stigmas than flowers from trees in pastures (52.1 vs. 32.3%, respectively). We also found that trees from continuous forests were almost six times more likely to set fruits and produce more seeds per fruit than trees in pastures. Morever, progeny from trees in continuous forests were, on average, more vigorous than the progeny from trees in pastures, as indicated by 12 of 16 indicators of plant vigor. However, there was no significant difference in the multilocus estimate of the outcrossing rate between the two groups of trees (tm = 1.00 and 0.99 for trees from continuous forest and trees from pastures, respectively). But there are differences in the correlation of paternity between the progeny of the two groups, where the progeny from trees in pastures showed a lower correlation of paternity than progeny of trees from continuous forests (r(p) = 0.104 and r(p) = 0.189, respectively). We argue that the mechanisms that regulate progeny vigor are disrupted in trees from pastures. We discuss the implications of these findings for the conservation of E. cyclocarpum.