Effects of tropical dry fragmentation on progeny vigor of Ceiba aesculifolia (Bombacaceae)

AGUILAR-ANGUIANO, JOSEFA, HERRERIAS-DIEGO, Y., AGUILAR R., ASHWORTH L. & QUESADA M.

Morelia, Mexico.

Congreso; Annual Meeting Association for Tropical Biology and Conservation; 2007

Centro de Investigaciones en Ecosistemas, Universidad Nacional Autonoma de Mexico.

Tropical dry forests are probably the most threatened systems in the tropics.Fragmentation studies in tropical dry forests indicate that certain characteristics of these ecosystems can affect the establishment of the secondary forest. In addition fragmentation can have negative effects on the reproductive success of plants, pollinator activity, and/or seedling establishment and survivorship. We evaluated the effects of habitat fragmentation on seedling vigor of the tree Ceiba aesculifolia (Bombacaceae) in a Mexican tropical dry forest. We compared progenies of parental trees located in two habitat conditions: (1) fragmented tree populations in disturbed areas with 1 to 2 reproductive individuals per hectare and surrounded by agricultural fields or pastures and (2) non-fragmented tree populations of 5 or more reproductive individuals per hectare surrounded by undisturbed mature forest. Seeds were planted in a greenhouse and the following parameters were evaluated for each seedling in both habitat conditions: 1) probability of seed germination, 2) probability of seedling survivorship 7 days and 3) 180 days after germination, 4) relative growth rate (RGR) 5) biomass 6) developing time of the first leaf and 7) final seedling height and number of seedling leaves. Seeds obtained from fragmented tree populations were more likely to germinate than seeds from continuous populations. Seedling survivorships (7 or 180 days after germination) were not affected by habitat condition. The RGR obtained for seedlings belonging to trees was approximately 0.8, indicating that Ceiba aesculifolia presents a quick growth in both habitat conditions. There were not significant differences between the developing time of the first leaf, seedling height, number of seedling leaves and biomass. We found a significant effect of maternal identity and seed weight on probability of seed germination and time of germination. Effects of fragmentation on germination will eventually have implications on seedling recruitment and populations demography of Ceiba aesculifolia.