Galen B. Rathbun

The San Joaquin Desert of California: Ecologically Misunderstood and Overlooked

ABSTRACT: The vegetation community of the San Joaquin Valley of California has been formally classified as a perennial grassland based largely on assumptions of past climax state. However, historical records suggest that the region might be more accurately classified as a desert. The distinction is important in determining the appropriate management strategies for this ecosystem, particularly for the many rare and endemic taxa that reside there. Abiotic and biotic factors—including low precipitation, arid soils, and desert-adapted plants and vertebrate—are consistent with conditions typical of desert areas. We examined the distributions of these factors to define the extent of the San Joaquin Desert. We conclude that the San Joaquin Desert historically encompassed 28,493 km2 including the western and southern two thirds of the San Joaquin Valley, and the Carrizo Plain and Cuyama Valley to the southwest. However, this ecosystem has been reduced by up to 59% from agricultural, industrial, and urban activities. The conservation of the unique biodiversity of this region is dependent upon this ecosystem being appropriately managed as a desert and not as a perennial or annual grassland.

A new species of round-eared sengi (genus Macroscelides) from Namibia

Abstract While studying the systematics and taxonomy of round-eared sengis (genus Macroscelides), we identified an unusual specimen from remote northwestern Namibia in the collection of the California Academy of Sciences. To determine if this represented a different species, we made 9 collecting trips with 5,616 trap-nights of effort that produced 16 voucher specimens (including the original specimen) of the unusual sengi. These specimens are distinguished from other Macroscelides species by morphological metrics (they are smaller), external features (rusty-tinged pelage, large subcaudal gland, and lack of dark skin pigment), and by divergence at 3 independently segregating DNA loci. These traits are the basis for the description of a new species of Macroscelides that seems to be confined to gravel plains associated with the distinctive reddish colored Etendeka geological formation of northwestern Namibia. The new species appears to be reproductively isolated from congeners, because portions of its distribution are sympatric with that of the Namib round-eared sengi (M. flavicaudatus), and we found no evidence of hybrid individuals or gene flow. The new species is allopatric with the Karoo round-eared sengi (M. proboscideus), which is found about 500 km to the south. The new species, along with M. flavicaudatus, is endemic to Namibia. With this 3rd species in the genus, there are now 19 recognized extant species in the order Macroscelidea.

Phylogeny and taxonomy of the round-eared sengis or elephant-shrews, genus Macroscelides (Mammalia, Afrotheria, Macroscelidea)

The round-eared sengis or elephant-shrews (genus Macroscelides) exhibit striking pelage variation throughout their ranges. Over ten taxonomic names have been proposed to describe this variation, but currently only two taxa are recognized (M. proboscideus proboscideus and M. p. flavicaudatus). Here, we review the taxonomic history of Macroscelides, and we use data on the geographic distribution, morphology, and mitochondrial DNA sequence to evaluate the current taxonomy. Our data support only two taxa that correspond to the currently recognized subspecies M. p. proboscideus and M. p. flavicaudatus. Mitochondrial haplotypes of these two taxa are reciprocally monophyletic with over 13% uncorrected sequence divergence between them. PCA analysis of 14 morphological characters (mostly cranial) grouped the two taxa into non-overlapping clusters, and body mass alone is a relatively reliable distinguishing character throughout much of Macroscelides range. Although fieldworkers were unable to find sympatric populations, the two taxa were found within 50 km of each other, and genetic analysis showed no evidence of gene flow. Based upon corroborating genetic data, morphological data, near sympatry with no evidence of gene flow, and differences in habitat use, we elevate these two forms to full species.

Late Pleistocene Potential Distribution of the North African Sengi or Elephant-Shrew Elephantulus rozeti (Mammalia: Macroscelidea)

The Sahara Desert was recently proposed as the agent of vicariant speciation in the North African elephant-shrew (order Macroscelidea, Elephantulus rozeti). Based on evidence from molecular dating, however, this speciation event was estimated as having occurred in the Miocene, an early date of origin for an extant species, predating the dramatic climatic fluctuations of the Pleistocene. Here, we explore the possibility of more recent connections of populations of this species across the Sahara Desert that would have facilitated faunal exchange through the Last Glacial Maximum. We used ecological niche modelling based on current climatic datasets and known occurrence points to develop models of present-day potential distributions of E. rozeti and related taxa. Given that the Miocene scenario was proposed based on a single set of evidence, we here provide a partial test based on an independent analysis of present and past potential distributions. Our results corroborate the idea of vicariance, but indicate that distributional patterns and ecological characteristics are consistent with a more recent, post-Pleistocene vicariance across an increasingly arid Sahara. We emphasize the importance of multiple sets of evidence to be brought to bear on complex biogeographical questions, and offer models of palaeoclimatic and palaeoecological distributions and independent sources of such information to complement molecular systematic studies.

Home Range and Habitat Use by Blunt-nosed Leopard Lizards in the Southern San Joaquin Desert of California

Abstract We used radiotracking to study the home range and use of space by Blunt-nosed Leopard Lizards (Gambelia sila) in the Lokern Natural Area in the San Joaquin Desert of California. The average home-range size of males, based on the fixed kernal local convex hull method, was 6.21 ha in 2003 and 7.62 ha in 2004, which differed significantly from the average size for females, which was 2.85 ha in 2003 and 3.17 ha in 2004. Average home-range size did not differ significantly between years or with the interaction of sex and year. Home ranges of nine lizards with collars were in about the same locations between 2003 and 2004. There were no significant differences in either the percentage or number of home-range overlaps among adjacent pairs. Males moved an average of ∼100 m daily, significantly farther than the 65-m average daily movements of females, but there were no significant differences for the average greatest distance moved in 1 day by sex or year, or their interaction. The longest distance moved in a day for a male was 615 m and for a female was 642 m. We found that home ranges of Blunt-nosed Leopard Lizards contained more area of saltbush (Atriplex spp.) than expected based on proportion of area, but home-range sizes and distances moved did not differ significantly based on shrub presence.

Preliminary observations on home ranges and natural history of Scotinomys teguina in Costa Rica

Abstract We conducted a brief radiotelemetry study of Scotinomys teguina (Alston’s singing mice) in Costa Rica to better understand their natural history and spatial ecology. We radio-collared five mice, one of which was quickly eaten by a pitviper. The home ranges of the remaining mice were in moist habitats and ranged from 255 to 1620 m2, with extensive overlap between adjacent individuals. Singing mice, being small, diurnal, uniformly dark-colored insectivores foraging in dense forest floor habitats, have an adaptive syndrome similar to soricids, which may be due to the low diversity of shrews through Central America.

Reconstructing the molecular phylogeny of giant sengis (Macroscelidea; Macroscelididae; Rhynchocyon)

Giant sengis (Macroscelidea; Macroscelididae; Rhynchocyon), also known as giant elephant-shrews, are small-bodied mammals that range from central through eastern Africa. Previous research on giant sengi systematics has relied primarily on pelage color and geographic distribution. Because some species have complex phenotypic variation and large geographic ranges, we used molecular markers to evaluate the phylogeny and taxonomy of the genus, which currently includes four species: R. chrysopygus, R. cirnei (six subspecies), R. petersi (two subspecies), and R. udzungwensis. We extracted DNA from fresh and historical museum samples from all taxa except one R. cirnei subspecies, and we generated and analyzed approximately 4700 aligned nucleotides (2685 bases of mitochondrial DNA and 2019 bases of nuclear DNA) to reconstruct a molecular phylogeny. We genetically evaluate Rhynchocyon spp. sequences previously published on GenBank, propose that the captive R. petersi population in North American zoos is likely R. p. adersi, and suggest that hybridization among taxa is not widespread in Rhynchocyon. The DNA sample we have from the distinctive but undescribed giant sengi from the Boni forest of northern coastal Kenya is unexpectedly nearly identical to R. chrysopygus, which will require further study. Our analyses support the current morphology-based taxonomy, with each recognized species forming a monophyletic clade, but we propose elevating R. c. stuhlmanni to a full species.

Home range and use of diurnal shelters by the Etendeka round-eared sengi, a newly discovered Namibian endemic desert mammal.

To understand habitat use by the newly described Etendeka round-eared sengi (Macroscelides micus) in northwestern Namibia, we radio-tracked five individuals for nearly a month. Home ranges (100% convex polygons) in the rocky desert habitat were remarkably large (mean 14.9 ha) when compared to sengi species in more mesic habitats (<1.5 ha). The activity pattern of M. micus was strictly nocturnal, which contrasts to the normal diurnal or crepuscular activity of other sengis. The day shelters of M. micus were under single rocks and they likely were occupied by single sengis. One tagged sengi used 22 different day shelters during the study. On average, only 7% of the day shelters were used more than once by the five tagged sengis. The shelters were also unusual for a small mammal in that they were unmodified in terms of excavation or nesting material. Shelter entrances were significantly oriented to face south by south west (average 193°), away from the angle of the prevailing midday sun. This suggests that solar radiation is probably an important aspect of M. micus thermal ecology, similar to other sengis. Compared to published data on other sengis, M. micus generally conforms to the unique sengi adaptive syndrome, but with modifications related to its hyper-arid habitat.

Water Temperatures in a California Red-legged Frog Breeding Pond

The California Red-legged Frog ( Rana draytonii ) is a threatened species, thus resource managers are faced with maintaining, and even creating, breeding habitat for the frog. The Mediterranean climate regime where the frog occurs can result in breeding site desiccation during the long dry summer, before larval metamorphosis occurs, which can be exacerbated in coastal areas where prevailing cool temperatures might slow tadpole development. Water temperature profiles were logged every three hours for six days at a coastal breeding pond. Despite mid-day maximum air temperatures that averaged about 14 o C, solar radiation produced mid-day shallow-water temperatures approaching 30 o C. These preliminary data hopefully will encourage further research on the topic, but in the meantime will assist resource mangers to better understand frog behavior and existing recommendations for maintaining, improving, and developing frog breeding habitat.