D h benzing h luther and b bennett

Reproduction is central to the evolutionary theme of this volume, but an uneven literature precludes a balanced treatment. Numerous reports deal with issues like pollination, while a host of other subjects (e.g., breeding systems) remain largely ignored. Reasons for the disparity range from botanical tradition to differences in the ease and costs of pursuing speci c kinds of inquiry. Publications on ower, fruit and seed structure exceed all others on bromeliad reproduction to the extent that even a reasonable overview of this material requires a separate chapter (Chapter 3). Issues such as seed dispersal and gene ow and demography, along with the other phenomena that in uence reproductive success and evolution, receive rst priority here.

A single, fundamental bauplan and life under often stressful growing conditions help explain why most Bromeliaceae share several de ning aspects of natural history. Life cycles usually proceed slowly and several years to decades pass before the typical bromeliad produces the rst of usually multiple seed crops (iteroparity) from branched, determinant shoots (Fig. 2.3). About half a dozen genera in Pitcairnioideae and Tillandsioideae also include one or more members that fruit just once (the monocarps) after some 15 to many additional years devoted solely to resource accumulation (Figs. 2.3B, 14.2C). Genets of the iteroparous types that survive long enough fragment into multiple, autonomous units, and especially successful genets of the most aggressive terrestrials dominate extensive habitat (e.g., Brokaw 1983; Murawski and Hamrick 1990).

Numerous less routine aspects of reproduction and life history accommodate speci c Bromeliaceae to speci c kinds of ecospace and growing conditions. Fruit and seed morphology indicate dispersal by wind, perhaps owing water, several groups of vertebrates, ants and possibly some other invertebrates. Breeding systems and pollinators also distinguish

Was this article helpful?

0 0

Post a comment