Geology topics

Walter E. Meshaka

Publications and source records attributed to Walter E. Meshaka.

3 recordsLinked to original sources

USGS2021

Demographic responses to density-dependence by two populations of the Florida Tree Snail, Liguus fasciatus (Gastropoda: Orthalicidae), in Everglades National Park

D uring May-October 1996, we captured and individually marked and released Florida Tree Snails, Liguus fasciatus, from two sites, a subclimax hammock and a large isolated wild tamarind tree, in the Long Pine Key region of Everglades National Park. Populations shared the same two dominant morphs, castaneozonatus and. cingulatus, both of which are strong colonizers. Monthly survivorship between the two sites were comparable, although annual survivorship was lower on the isolated tree. Intersite differences in growth rates were equivocal. The populations differed with respect to number of morphs, population size, and population structure. The hammock site was a subclimax hammock with a large and stable bell-shaped population structure comprising nine morphs. In contrast, the population structure of the single tree was highly skewed, with many young individuals produced, intermediate ages absent, and few large adults of larger asymptotic size present. Number of snails/m was higher on the isolated tree. Demographic studies of the Florida Tree Snail are uncommon. Our findings corroborate certain aspects of the ecology of this species and clarify two different demographic responses, one of stability, and one of apparent resource limitation whose demography represents opportunities for colonization.

Florida↗

USGS2019

The effects of geography, habitat, and humans on the ecology and demography of the Gopher tortoise ( Gopherus polyphemus ) in the southern Lake Wales Ridge region of Florida

A 35-year (1967–2002) demographic study was conducted on the gopher tortoise (Gopherus polyphemus) from two different habitats on Archbold Biological Station located on the southern end of the Lake Wales Ridge in south-central Florida. We found geographic, habitat, and human-mediated effects on several aspects of its biology. Our findings underscore the necessity of long-term demographic data to more accurately answer ecological questions concerning long-lived species, such as how the gopher tortoise detectably might be affected by habitat quality and human activities.

Florida↗

USGS2012

Severe mammal declines coincide with proliferation of invasive Burmese pythons in Everglades National Park

Invasive species represent a significant threat to global biodiversity and a substantial economic burden. Burmese pythons, giant constricting snakes native to Asia, now are found throughout much of southern Florida, including all of Everglades National Park (ENP). Pythons have increased dramatically in both abundance and geographic range since 2000 and consume a wide variety of mammals and birds. Here we report severe apparent declines in mammal populations that coincide temporally and spatially with the proliferation of pythons in ENP. Before 2000, mammals were encountered frequently during nocturnal road surveys within ENP. In contrast, road surveys totaling 56,971 km from 2003–2011 documented a 99.3% decrease in the frequency of raccoon observations, decreases of 98.9% and 87.5% for opossum and bobcat observations, respectively, and failed to detect rabbits. Road surveys also revealed that these species are more common in areas where pythons have been discovered only recently and are most abundant outside the python's current introduced range. These findings suggest that predation by pythons has resulted in dramatic declines in mammals within ENP and that introduced apex predators, such as giant constrictors, can exert significant top-down pressure on prey populations. Severe declines in easily observed and/or common mammals, such as raccoons and bobcats, bode poorly for species of conservation concern, which often are more difficult to sample and occur at lower densities.

Florida↗