Abstract

Agassiz's desert tortoise, Gopherus agassizii, faces threats from climate change. With limited mobility to move long distances to more-suitable habitat as climate change advances, whether protecting tortoises in situ or translocating them out of harm's way, a critical conservation task is identifying refugia, lands that will remain suitable under the current climate and the projected, end of the 21st Century warming and drying. While researchers have modeled tortoise habitat suitability, they have done so at coarse scales and did not identify climate refugia that may become apparent only with a fine-scale approach. It is at that scale that managers can implement measures that will foster habitat protection for tortoises throughout their current range. In this case study, we employed fine-scale habitat suitability modeling to identify current habitat and climate refugia within and surrounding the Marine Corps Air Ground Combat Center (MCAGCC) at Twentynine Palms, California. We modeled nearly 284,000 ha of currently suitable tortoise habitat within an 858,800-ha study area. Projected maximum end-of-the-century summer temperatures could reduce the area of tortoise habitat 55% to 127,650 ha; however, almost 115,800 ha would overlap current tortoise habitat and would serve as climate refugia. Applied elsewhere, where tortoise protection must be balanced with other land uses, this approach could increase the efficacy of conservation for this threatened species. Nevertheless, until validated with field studies, habitat suitability models represent hypotheses as to current and future distributions of appropriate tortoise habitat. These hypotheses should foster additional research identifying whether tortoise densities and demographic structure are more secure and whether tortoises can adapt to shifting climates more effectively within than outside modeled refugia.

Abstract

In contrast to the other Podocnemis species, Podocnemis erythrocephala (Pleurodira: Podocnemididae) is restricted to blackwater and clearwater rivers and lakes, including the Negro River basin, and several other tributaries of the eastern Amazon River basin. In order to test the effects of geographic barriers on genetic connectivity of P. erythrocephala, 10 localities sampled throughout the Brazilian Amazon basin were studied. Two hundred and forty-six specimens were sequenced for the mitochondrial control region. Analysis of molecular variance confirmed the existence of population subdivision (Φ _ST = 0.28, p < 0.001). In pairwise comparisons, the values of the fixation index Φ _ST were significant in almost all comparisons involving the São Gabriel da Cachoeira (Negro River), Jaú National Park (Jaú River), and Barreirinha (Andirá River), indicating that these populations are genetically differentiated. Genetic differentiation is most likely explained by the presence of rapids and waterfalls separating the São Gabriel da Cachoeira (Negro River) and Jaú National Park (Jaú River) populations from the remaining populations. Populations from Barreirinha (Andirá River) were also genetically differentiated, providing support for the hypothesis that the Amazon River is a geographic barrier for this species. Although distributed over a large geographic area, the remaining 7 localities were not differentiated from one another (p > 0.005), suggesting that these localities are part of a panmictic population distributed throughout the central Amazon basin. We recommend that the 4 structured populations be treated as separate management units.

Abstract

Fossils from paleocoastal deposits in northwestern Florida represent at least 3 pleurodire taxa. Biochronologic and paleoclimatic correlates suggest that the presence and absence of side-necked turtles in Florida was synchronous with global climatic shifts in the middle to late Paleogene and early Neogene. The oldest pleurodire record in Florida is from the end of the Greenhouse World in the middle to late Eocene, followed by a hiatus of ∼ 11 million yrs during the onset of the Icehouse World in the early Oligocene. Their sojourn in Florida during the latest Oligocene (25–24 Ma) was concurrent with a brief late Oligocene warming (LOW), and a subsequent hiatus in the early Miocene (∼ 24–18 Ma) was contemporaneous with global cooling. Their resettlement and most populous occurrences in Florida during the middle to late Hemingfordian through early Barstovian (∼ 18–15.5 Ma) coincided with the Middle Miocene Climatic Optimum (MMCO), a significant global warming event. Pleurodires are indicators that paleoclimate in the southeastern United States was frost free during the Eocene, LOW, and MMCO with air and water temperatures warm enough to support these generally cold-intolerant turtles. A small-bodied podocnemidid existed in the Cucaracha Formation (∼ 19.05–18.8 Ma) of Panama during the early Miocene pleurodire hiatus in Florida, and this or a closely related taxon later dispersed into Florida by the early Barstovian, when temperatures were suitable during the MMCO. Previously reported pleurodire fossils from the temporally mixed Lee Creek Mine of North Carolina are most likely middle Miocene in age when pleurodires were common in the Atlantic Coastal Plain of the southeastern United States. The presence of pleurodires in the Seaboard Local Fauna could help constrain the age of the fauna to younger than 18 Ma and probably closer to 17 Ma based on hypothesized paleoclimate at that time. A pleurodire from the middle Eocene Point “A” Dam site in southern Alabama may represent a late occurrence of the Bothremydidae.

Editorial Introduction. — This section is devoted to poetry involving turtles, representing either reprinted previously published or new unpublished material. We encourage our readers to submit poetry or songs for consideration, either their own material or work by other authors. Poems may be submitted to Anders G.J. Rhodin, Chelonian Research Foundation, E-mail: RhodinCRF@aol.com.

Our desire is to share with our readers the beauty and wonder of turtles as expressed through the art of the poem or song. In the sense that the relationship between man and turtles is multifaceted, so too is turtle poetry. The poems we