Reading the tree leaves

Natural History, April, 2003

Egbert Giles Leigh Jr. and Christian Ziegler ["Biosphere III" 2/03] make the important observation that the interplay between plant and animal species is central to shaping the diversity of tropical forests. Their study of the fragmentation of a Panamanian forest shows that the elimination of some animal species can dramatically alter the survival of certain plants and the composition of species.

Unfortunately, similar "experiments" are taking place throughout the Tropics: more than 60,000 square miles of forest are lost each year, creating a patchwork of unconnected fragments. Studies such as Messrs. Leigh and Ziegler's underscore the value of preserving large tracts of land, and of considering such a web of interactions in making decisions about forest management and conservation. Now is the time to make these critical land-use decisions before too much of what they aptly call a magic web is lost.

Phyllis D. Coley and Thomas
    A. Kursar
University of Utah
Salt Lake City, Utah

Messrs. Leigh and Ziegler offer an intriguing discussion of the unintended consequences of the building of the Panama Canal. That an "upscale" rainforest could be reduced in ninety years to a Jurassic-like, low-rent district in terms of biodiversity is instructive. Public works projects in the United States offer similarly dramatic examples of these inadvertent experiments in ecology. Lake Powell and Lake Mead comprise 500 square miles of lake where once "a river ran through." Now fish swim around in Anasazi ruins, and exotic vegetation and invader species of mollusk blur the natural order, creating a biological cacophony where once a desert symphony played. But there's a bright side: electric power galore. Now we can catch the nature channels in Phoenix and see the lights of Las Vegas from space.

Daniel J. Lenihan
National Park Service
Submerged Resources Center
Santa Fe, New Mexico

I am not so sure, as Messrs. Leigh and Ziegler maintain, that more than 150 million years ago there were no mutualistic associations between plants and animals analogous to the ones observed today. In late Pennsylvanian deposits (beginning about 298 million years ago), in which plant tissues are preserved in considerable anatomical detail, there is evidence for intricate associations. One example, from the Calhoun Flora of Illinois, is a seed fern that bears prepollen (a kind of microspore) far bigger than any known wind-dispersed pollen. The prepollen was produced in large organs that were evidently pierced by a large piercing-and-sucking insect. Furthermore, fecal pellets in the same deposit contain the same or similar prepollen. Do such findings simply point to pollen eating, or was the insect providing a mutualistic benefit to the plant as well?

Conrad C. Labandeira
Smithsonian Institution
Washington, D. C.