Earl D. McCoy’s research while affiliated with University of South Florida and other places

Theoretically, small, isolated populations should not persist. Empirically, this predication appears to be supported in some cases and contradicted in others. Although small population size is a central concept in conservation biology, it is not defined consistently in a biologically meaningful way. Its definition can be arbitrary (e.g., population sizes associated with quasi-extinction risk), driven by Allee thresholds, or assumed tied to minimum viable population size. Published values of small populations range from 20 to 100 000 individuals. Here, we review the concept of small population size, including how one might identify it using risk-based and recovery-based approaches, both of which define smallness functionally. Ideally, we want an approach that is both predictive and practical, but it is not clear that both can be had. We emphasize the important effects of density and dispersion on the risk and performance of populations, effects that tend to be ignored. We suggest that small applied to biological populations is a multifaceted concept, and that no single definition is likely to capture all the complexity. In which case, neither risk-based methods of identifying small populations nor recovery-based methods alone will suffice. We propose a framework that offers several definitions of small population size based on function (i.e., behavior of the population), each of which is sufficient for defining a small population. From expected smallest to largest estimated threshold population size: (1) The population’s behavior is dominated by demographic stochasticity. (2) The population has crossed an Allee threshold, exhibiting negative growth because of a behavioral mechanism inherent in the species. (3) The population has declined to the minimum persistent population size as revealed by a stochastic, simulation model, omitting threats and mitigation. (4) The population is unresponsive to threat mitigation. Although this method results in a designation of small populations that is both functional and biologically meaningful, the systematic study of the dynamics of small populations across taxa, and across density and dispersion within taxa, will create a more nuanced understanding of extinction risk. Ultimately, developing a predictive, recovery-based understanding of small-population dynamics will help link the small-population and declining-population paradigms, and improve species management planning.

Philosophers, policymakers, and scientists have long asserted that ecological science – and especially notions of homeostasis, balance, or stability – help to determine environmental values and to supply imperatives for environmental ethics and policy. We argue that this assertion is questionable. There are no well developed general ecological theories having predictive power, and fundamental ecological concepts, such as ‘community’ and ‘stability’, are used in inconsistent and ambiguous ways. As a consequence, the contribution of ecology to environmental ethics and values lies more in the realm of natural history and case studies than in the realm of general theory. Moreover, although general ecological theory is unable to contribute to environmental values in the way many philosophers and policymakers have hoped, environmental values can and do contribute to ecological hypotheses and methods. Using examples related to preservation versus development, hunting versus animal rights, and controversies over pest control, we show that, because ecology is conceptually and theoretically underdetermined, environmental values often influence the practice of ecological science.

Conservation schemes typically place species into categories, ranging roughly from rare to common or from vulnerable to least concern. Although a species may not be categorized as rare or vulnerable, it still may be sensitive to environmental change and, therefore, at risk of decline. To illustrate the importance of determining species sensitivity, we documented the relative sensitivities of four species of tree frogs, none of which have been designated particularly rare or vulnerable, to environmental change. Our research was conducted in central Florida, where prior research had suggested that Dryophytes femoralis and Dryophytes gratiosus were more sensitive to environmental change than Dryophytes cinereus and Dryophytes squirellus. A comparison of species characteristics and a field study of local abundances supported the dichotomy. Particularly, important environmental factors affecting the two more‐sensitive species adversely appear to be habitat selectivity, at a smaller scale, and nearness to the species’ southern range limits, at a larger scale. We suspected that one of the more‐sensitive species, D. gratiosus, is particularly sensitive to environmental change and that the cause is related to reproduction and/or growth. A series of laboratory analyses suggested strongly that the realized production of adults was less for D. gratiosus than for D. femoralis. Despite their identical placement in categorization schemes, the four species exhibited substantial differences in sensitivity to environmental change. A strong case can be made that the degree of sensitivity of D. gratiosus warrants increased conservation attention for the species. Our results indicate the potential value of field work and the generation of species‐specific information in improving categorization schemes, of broadening the categorization criteria typically employed, to accommodate sensitivity to environmental change, and of considering geographical scale in categorization schemes more than is done at present.

Oviductal sperm storage occurs in most squamate lineages, as well as in Tuatara. It is hypothesized to confer fitness benefits by increasing opportunities for reproductive success. These opportunities are specific to each selective landscape, but all are constrained by an underlying requisite phenotype, the duration that sperm can be stored and remain viable. Functional sperm storage durations are generally estimated by field observations of reproductive ecology or the presence of sperm in the oviduct, with few direct tests of sperm viability over time or reproductive events. In sceloporine lizards of the family Phrynosomatidae, functional sperm storage has been examined in many viviparous species with asynchronous reproduction, but oviparous species with synchronous reproduction have not been examined. We assessed functional sperm storage in two oviparous sceloporine lizards with synchronous reproduction, the Eastern Fence Lizard (Sceloporus undulatus) and the Florida Scrub Lizard (S. woodi). Over a 4-mo period of isolation, we found reproductive success of gravid females declined in both species (3.9% per week in S. undulatus and 6.7% in S. woodi), although moderate levels of fertility and hatching success were observed for up to 12 weeks in S. undulatus and 14 weeks in S. woodi. Our data suggest, for these populations, that functional sperm storage occurs across the reproductive season, but is unlikely to continue into the next year.

OBJECTIVES: Here, we present the results of a study that used radiotelemetry to track the movements of H. gratiosa adults migrating (see Semlitsch 2008) away from a west-central Florida breeding site. Although this study was conducted in the late 1990s and followed only a small number of individuals at a single site—a problem that is typical for studies of uncommon species (see Freda and Gonzalez 1986; Richter et al. 2001)—the information obtained has taken on increased significance in the face of the unbridled expansion of development and its associated landscape alteration in Florida, which has continued into the 2020s.

How have we managed to maintain our research partnership for more than 30 yr? We have come to think that personal respect for one another and trust that our core values and motivations are immutable have been key. Our partnership began with a project to gather much-needed information on Gopherus polyphemus (Daudin) (Gopher Tortoise). We soon realized that the species was in peril. The enormous pressures put upon species and habitats by the exploding human population of Florida fueled our desire not only to accumulate information about basic biology and ecology, but also information relevant to effective conservation and management. Our interest in the Gopher Tortoise expanded naturally to other inhabitants of the xeric uplands, particularly Plestidon reynoldsi Stejneger (Florida Sand Skink). This species inhabits the pyrogenic scrub habitat on the central ridges, which has been mostly lost to development. We present previously unpublished data that cautiously suggest that clear-cutting would be an effective tool for managing small habitat fragments when burning is not a reasonable option. Although we have worked closely with businesses and agencies, we understand that their motivations for facilitating conservation research are not necessarily the same as our motivations for conducting the research; however, we would not have been able to accomplish what we have without the cooperation and support of these entities. Regardless, destruction of xeric uplands has continued apace, and our inability to forestall species' decline is the most frustrating aspect of our partnership. Despite our frustration, we remain motivated by our conviction that we are doing the right thing.