Evolutionary and ecological response of pocket gophers (Thomomys talpoides) to late-Holocene climatic change

Late-Holocene evolutionary and ecological response of pocket gophers ( Thomomys talpoides ) and other species to climatic change is documented by mammalian fossils from Lamar Cave, a palaeontological site in northern Yellowstone National Park. Pocket gophers illustrate ecological sensitivity to a series of mesic to xeric climatic excursions in the sagebrush-grassland ecotone during the last 3200 years, increasing in abundance during mesic intervals, and declining in abundance during xeric intervals. Four other small mammal taxa (Microtus sp., Peromyscus maniculatus, Neotoma cinerea and Spermophilus armatus) also show response to climatic change, increasing or decreasing in abundance in accordance with their preferred habitat requirements. To determine evolutionary response to climate, two craniodental characters for the northern pocket gopher ( Thomomys talpoides ) are investigated in modern representatives within a 400 km radius of Lamar Cave and then tracked through the time spanned by the fossils. One morphologic character shows that variation in body size, primarily a plastic response to the environment, demonstrates few taxonomically consistent patterns of geographic variation across 39 modern localities. In contrast, the other character indicates genetic relatedness within subspecies. Stasis in the genetically controlled character indicates that the same subspecies of pocket gopher ( T. talpoides tenellus ) has occupied northern Yellowstone for at least 3200 years. However, T. t. tenellus does show plastic response to climatic change because pocket gophers during the Medieval Warm Period were smaller than at any other time spanned by the deposit.     

Zur genetik der 6-Phosphogluconatdehydrogenase (EC:1.1.1.44) bei Säugern

Zusammenfassung Das Enzym 6-PGD zeigt bei den verschiedensten Species einen genetisch gesteuerten Polymorphismus, der sich bei elektrophoretischer Darstellung in einer Variabilität des Isoenzymmusters äußert. Die Befunde bei den bislang untersuchten Säugern unter Einschluß des Menschen lassen sich formalgenetisch nach dem Modell: 1 Genlocus mit multipler Allelie interpretieren. Zur Prüfung der Frage, ob das Säugergenom einheitlich nur ein Gen für dieses Enzym enthält oder ob bei einzelnen Species eine Duplikation dieses Gens existiert, wurdene eine Anzahl Säuger verschiedener Ordnungen untersucht. In einer ersten Mitteilung wird hier über 6 verschiedene Species der Microtinae berichtet. Die Befunde sprechen durchweg für die Existenz von jeweils nur 1 Genlocus der 6-PGD. Bei Microtus oeconomus wurden 2 Allele an diesem locus nachgewiesen, bei Microtus ochrogaster 3 verschiedene Allele. Durch Familienuntersuchungen bei diesen beiden Species werden alle möglichen Kombinationen dieser Allele nachgewiesen.

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The genetics of 6-PGD (EC: 1.1.1.44) in various mammals I. Studies on 6 species of Microtinae, Rodentia. Isoenzyme polymorphism and family studies in Microtus oeconomus and Microtus ochrogaster

Summary The enzyme 6-PGD exhibits a genetically determined polymorphism which results in a variability of the isoenzyme pattern. In mammals so far examined the findings are to be interpreted according to the model of multiple alleles at one single gene locus. In order to test whether the mammalian genome is uniformly endowed with one single locus for this enzyme or whether a duplication of this locus is present in certain species, we examined various mammals of different orders. Our results in this first communication on 6 different Microtinae species are all in agreement with the assumption of a single 6-PGD locus. In Microtus oeconomus 2 alleles could be demonstrated and in Microtus ochrogaster 3 different alleles. Family studies performed with both species revealed the occurrence of all the expected combinations of these alleles.

     

Is the loss of Australian digging mammals contributing to a deterioration in ecosystem function?

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Effects of small mammal and invertebrate herbivory on plant species richness and abundance in tallgrass prairie

Summary A factorial field experiment was designed to test the effects of small mammals and above- and below-ground invertebrates on plant species richness and composition in native tallgrass prairie at Konza Prairie Research Natural Area, northeast Kansas. Over a 4-year period, Microtus ochrogaster densities were maintained by live-trapping in fenced plots, and invertebrate levels were reduced using the pesticides carbaryl for above-ground invertebrates and an organophosphate (isofenphos) for belowground invertebrates. ANOVA according to a split-plot design of plant species biomass data harvested in 1984 and 1986 revealed few significant effects of either small mammal densities or pesticide application. Of 54 species harvested from both sample dates, only 10 were significantly affected by either treatment. Analysis of species richness according to 8 life-form classes provided a clearer pattern of response than did biomass either by species or life-form class. For example, numbers of C4 grasses were reduced by increasing small mammal densities, whereas numbers of C4 annual forbs were lowest when above-ground herbivory was reduced. While consumers have been shown to have strong effects on successional communities, the few significant results observed in this study suggests that the manipulated levels of small mammals and insects had few effects on a mature tallgrass prairie.Deceased May, 1986     

Effects of conspecific and heterospecific residents on patterns of immigration in two species of voles

Studies with birds have shown that presence and density of resident conspecifics and heterospecifics can influence patterns of habitat selection. There have been few studies on the effects of social cues on rates of immigration in mammals. We report results from a long-term live trapping study of immigration in two species of voles, Microtus ochrogaster Wagner, 1842 and Microtus pennsylvanicus Ord, 1815, in bluegrass habitat in east-central Illinois, USA. We compare immigration into control sites from which no individuals of either species were removed with immigration into experimental sites from which either conspecifics or heterospecifics were removed. We focus on characteristics of immigrants and rates of immigration in relation to density in destination habitats. Within each species, immigrants into control and removal sites were similar with respect to body mass and reproductive condition, indicating no major differences in the physical condition of immigrants into sites with established populations and sites without established populations. For both species, density of conspecifics at a site positively influenced rate of immigration at that site. Density of heterospecifics at destination sites did not significantly influence rate of immigration for either species. These results suggest that site selection by dispersing M. ochrogaster and M. pennsylvanicus is characterized by conspecific attraction.     

Documenting the biogeographic history of Microtus cabrerae through its fossil record

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Mammalian responses to Middle Holocene climatic change in the Great Basin of the western United States

In spite of decades of intense research directed toward understanding the climates and ecology of the Great Basin (western United States) during the past 10,000 years, the responses of mammals to the extreme aridity of the Middle Holocene (c. 8000–5000 years ago) in this region have been poorly understood. Using a well‐dated small mammal sequence from Homestead Cave, north‐central Utah, I show that the Middle Holocene small mammal faunas of this area underwent a decrease in species richness and evenness, driven largely by a series of local extinctions and near‐extinctions coupled with a dramatic increase in the abundance of taxa well‐adapted to xeric conditions. At the end of this period, some taxa that require relatively mesic habitats began to increase in abundance immediately, others did not rebound in abundance until several thousand years later, while still others have not returned at all. This suite of responses has been difficult to detect because climatic change at the beginning of the Middle Holocene was so much more substantial than that which occurred toward its end.     

Multiple captures provide evidence of small mammal social behavior

Social behavior of small mammals living under natural conditions often is inferred from live-trapping data, particularly from incidents in which two or more individuals are captured together in a trap. We examined whether multiple-capture data from a long-term study of prairie voles (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus) were consistent with well-known species differences in social behavior (whereas prairie voles are highly social and display monogamy, meadow voles are less social and promiscuous). When possible, we also examined multiple captures of two nontarget species, northern short-tailed shrews (Blarina brevicauda) and western harvest mice (Reithrodontomys megalotis). Percent of total captures that were multiple captures and percent of total adult captures that were male–female captures were highest for prairie voles and lowest for meadow voles; values for harvest mice and shrews were in between those of the vole species, but more similar to values for meadow voles. Repeat captures of the same male–female pair occurred most commonly in prairie voles, and multiple captures of this species typically involved individuals from the same social group. Multiple captures of adults and juveniles were more common in prairie voles than meadow voles, except for captures of at least one adult male and at least one juvenile, which did not differ between the two vole species. Multiple capture data for prairie voles and meadow voles were largely consistent with established species differences in social behavior, suggesting that such data can provide an accurate indication of social and mating systems of small mammals.     

Rodents and Insectivores from the Upper Miocene of Molayan, Afghanistan

Although Molayan is the richest fossil mammal locality in Afghanistan, only a few species have been studied. This paper describes three rodents (Hystrix aryanensis sp. nov., Parapeolomys sp. and Pseudomeriones latidens sp. nov.) and one insectivore (Erinaceus sp.). Lithostratigraphical correlations and biostratigraphical studies in the Khurdkabul Basin provide evidence that the Molayan locality is younger than three other localities in this basin: Sherullah, Taghar and Ghazgay. In addition, the taxa described here, along with several species of large mammals from Molayan, permit correlations with the Siwalik succession in Pakistan to the east, and with European Neogene mammal ages to the west. The age of the Molayan fauna is concluded to be mid Turolian. Observations on the mammal faunas from the Khurdkabul Basin suggest that the altitude of the area, at present over 2000 m, was much lower during the late Miocene. Uplift of the basin probably occurred no earlier than the ?late Pliocene.     

Cold-climate rodent indicators for the Late Pleistocene of Central Iberia: New data from the Buena Pinta Cave (Pinilla del Valle,Madrid Region,Spain)

In the Iberian Peninsula, the Late Pleistocene record of small mammal indicators of cold climates is largely restricted to two sets of sites at the eastern and western ends of the Pyrenees. Some assemblages from other sites at the Peninsular centre have, however, recently yielded such taxa. This work describes the remains of three such rodent species from the Buena Pinta Cave, a site in the Sierra de Guadarrama mountains in the Spanish Central System. Excavation campaigns in the cave have taken place every summer since 2003. Thermoluminescence analyses of sediments from levels 2–5 of the site suggest an age corresponding to the middle of the Late Pleistocene, within Marine Isotope Stage 4 or the beginning of Marine Isotope Stage 3. Sieve-washing and picking out of the small fossils contained in the sediments of levels 2–5 yielded several thousand small mammal teeth and other remains, dominated by Microtus arvalis. Smaller numbers of remains belonging to other rodents typical of cold climates were also identified, such as Microtus oeconomus, Microtus gregalis and Chionomys nivalis. Thus, the small mammal record of the Buena Pinta Cave shows that rodent indicators of cold climates reached the centre of the Iberian Peninsula during the mid-Late Pleistocene, i.e., well before the Last Glacial Maximum. These findings represent one of the southernmost Pleistocene records for M. oeconomus in Europe, and the most southerly for M. gregalis.     

The small mammals from the Holocene site of Guenfouda (Jerada,Eastern Morocco): chronological and paleoecological implications

The study of small mammals may provide important chronological and paleoenvironmental information in the archaeological context of a particular geographic region. Few specific studies have been conducted on fossil small mammals in North Africa, especially for the late Quaternary period. However, the Holocene site of the Guenfouda Cave, situated in the region of Oujda (Eastern Morocco), provides new data on the chronology and the paleoecology of this period. The small-mammal association from Guenfouda comprises at least 12 taxa: two soricomorphs (Crocidura russula and C. whitakeri), one macroscelian (Elephantulus rozeti), two bats (Myotis blythii and Rhinolophus hipposideros) and seven rodents (Mus spretus, Meriones shawii, Apodemus sylvaticus, Dipodillus campestris, Eliomys sp., Atlantoxerus getulus and Ctenodactylus sp.). The absence in our assemblage of species recently introduced to Morocco, such as Mus musculus and Rattus spp. (R. rattus and R. norvegicus), allows us to establish relative data for the beginning of the Holocene (Neolithic) for the Guenfouda Cave in accordance with the archaeological remains recovered. From a paleoecological point of view, the small-mammal assemblage shows a mosaic landscape dominated by a Mediterranean climate similar to today but slightly drier, comparable to that found in other sites in North Africa with an analogous chronology.     

Palaeozoological insights into management options for a threatened mammal: southern Africa’s Cape mountain zebra (Equus zebra zebra)

Aim Promoting population growth of genetically distinct subpopulations of Cape mountain zebra (Equus zebra zebra) is crucial to the survival of the subspecies. Several important Cape mountain zebra reserves are dominated by fynbos vegetation, and population growth is limited by a lack of grassland habitat. A fossil ungulate sequence spanning the last c. 18,000 years is examined to understand the long‐term history of this conservation challenge. Location Boomplaas Cave (BPA), South Africa. Methods The fossil sequence from BPA is examined to reconstruct ungulate community dynamics in relation to climate and vegetation change over the last 18,000 years. Results Ungulates from 18,000 to 12,000 years ago suggest an expansion of open grasslands that supported a grazing ecosystem dominated by an extinct caprine antelope and equid remains attributed to E. zebra and E. quagga. At the onset of the Holocene, the grazing ungulate community disappears and small browsers and mixed feeders dominate the assemblage, indicating the loss of open grassland vegetation. Several open‐habitat grazers go extinct at this time, and Equus persists at much lower abundances. This shift can be explained by global climate change across the Pleistocene–Holocene transition. Main conclusions The fossil sequence supports contemporary observations indicating that access to open grassland is crucial to maintaining large Cape mountain zebra subpopulations. Although fynbos is abundant throughout the historic range of the Cape mountain zebra, fossil evidence suggests that such vegetation is unlikely to support dense populations. It has been suggested that the acquisition of agricultural lands that were historically converted to open grasslands for livestock could promote Cape mountain zebra population growth. Results presented here support this management option, as the open grasslands in these converted landscapes likely approximate the vegetation structure during latest Pleistocene, when grasslands were widespread and grazing ungulates abundant.     

Threatened mammals become more predatory after small‐scale prescribed fires in a high‐rainfall rocky savanna

Understanding mechanisms underlying fire regime effects on savanna fauna is difficult because of a wide range of possible trophic interactions and feedbacks. Yet, understanding mechanisms underlying fauna dynamics is crucial for conservation management of threatened species. Small savanna mammals in northern Australia are currently undergoing widespread declines and regional extinctions partly attributable to fire regimes. This study investigates mammal trophic and ecosystem responses to fire in order to identify possible mechanisms underlying these declines. Mammal trophic responses to fire were investigated by surveying mammal abundance, mammal diet, vegetation structure and non‐mammal fauna dynamics in savannas six times at eight sites over a period of 3 years. Known site‐specific fire history was used to test for trophic responses to post‐fire interval and fire frequency. Mammal and non‐mammal fauna showed only minor responses of post‐fire interval and no effect of fire frequency. Lack of fauna responses differed from large post‐fire vegetation responses. Dietary analysis showed that two mammal species, Dasyurus hallucatus and Isoodon auratus, increased their intake of large prey groups in recently burnt, compared to longer unburnt vegetation. This suggests a fire‐related change in trophic interactions among predators and their prey, after removal of ground‐layer vegetation. No evidence was found for other changes in food resource uptake by mammals after fire. These data provide support for a fire‐related top‐down ecosystem response among savanna mammals, rather than a bottom‐up resource limitation response. Future studies need to investigate fire responses among other predators, including introduced cats and dingoes, to determine their roles in fire‐related mammal declines in savannas of northern Australia.     

Small mammals as potential reservoir hosts of <Emphasis Type="Italic">Babesia microti</Emphasis> in the Middle Urals

Using PCR and nested PCR methods, 382 blood samples from adult small mammals of 14 species were examined for Babesia microti. The mammals were trapped in the southern taiga of the Middle Urals (Chusovskoi district, Perm Region). The DNA of human babesiosis agent was detected in the blood of 172 small mammals (45.0% of the samples examined) of 11 rodent and insectivore species (Chlethrionomys glareolus, C. rutilus, C. rufocanus, Microtus oeconomus, M. agrestis, Myopus schisticolor, Apodemus uralensis, Sorex araneus, S. caecutiens, S. isodon, S. tundrensis). Especially high infection rates were characteristic of C. glareolus and S. araneus (47.1 and 38.2 %, respectively), the most abundant small mammal species in the study area. The results confirm the high frequency of contact of small mammals with B. microti in forest ecosystems of the Middle Urals and indicate that they probably maintain circulation of this pathogen.     

Translocations of digging mammals and their potential for ecosystem restoration: a review of goals and monitoring programmes

1. Globally, translocations are commonly used to improve the conservation status of threatened species. There is increasing recognition that translocations of ecosystem engineers also have the potential to restore ecological processes. Digging mammals are often considered to be ecosystem engineers, as their diggings provide shelter for other species and can significantly alter soil properties, with subsequent changes to vegetation.
2. Using Australian species as a case study, we reviewed published and grey literature on digging mammal translocations to determine how often these translocations are conducted to restore ecosystem processes. We documented ecosystem-level monitoring and research efforts, and assessed whether restoration was perceived to be occurring post-release.
3. At least 208 translocations of 24 digging mammal species have been conducted in Australia, with a further 38 planned for the near future. Prior to 2019, only 3% of translocations included a goal relating to the restoration of ecosystem processes associated with digging activities. Nearly a quarter of pre-2019 translocations have been the subject of some form of ecosystem-level monitoring or research, but long-term ecosystem-level monitoring was very rare. In contrast, 74% of the translocations planned for post-2018 include a goal relating to the restoration of ecological processes and most also include plans to conduct ecosystem-level monitoring.
4. Ecosystem restoration was perceived to be occurring for 26% of the pre-2019 translocations. None of the documents we reviewed indicated that ecological degradation had occurred post-translocation, even when declines in other taxa were recorded.
5. The restoration of ecosystem processes is increasingly being identified as a goal for translocation programmes. Where this is the case, we suggest that translocation practitioners include success criteria for the restoration of ecosystem processes, and commit to long-term monitoring designed to detect ecosystem-level effects of translocations.

     

Small mammal community ecology

Summary The abundance of food in natural 1-ha plot of shortgrass prairie was artificially manipulated by adding alfalfa pellets and whole oats on a regular schedule. The small mammal species naturally inhabiting the manipulated food plot did not respond in either their density or weight to the supplemented food. However, a new specialized seed-eating species, Dipodomys ordii, invaded the food plot and persisted in relatively high density. As a result of this colonization, species diversity was significantly higher on the food plot relative to the unmanipulated control plot. In a second experiment, application of water and nitrogen to two 1-ha plots of shortgrass prairie resulted in increased productivity. However, the increased production on this latter treatment was associated with vegetation growth and thus major changes in habitat structural characteristics relative to the control treatment. Two new species, Microtus ochrogaster and Reithrodontomys megalotis, colonized the nitrogen+water treatment, but other small mammal species resident to the shortgrass prairie largely avoided this treatment. As a result of this manipulation, species diversity was significantly lower than the species diversity on the control treatment. These two results agree with the MacArthur prediction regarding how species diversity responds to an increase in production of scarce resources without changes in other habitat variables, and to an increase in productivity associated with changes in other habitat variables.     

Small mammals cause non-trophic effects on habitat and associated snails in a native system

Legacy effects occur when particular species or their interactions with others have long-lasting impacts, and they are increasingly recognized as important determinants of ecological processes. However, when such legacy effects have been explicitly explored, they most often involve the long-term direct effects of species on systems, as opposed to the indirect effects. Here, we explore how a legacy of small mammal exclusion on the abundance of a shrub, bush lupine (Lupinus arboreus), influences the abundance of a native land snail (Helminthoglypta arrosa) in coastal prairie and dune habitats in central California. The factors that limit populations of land snails are very poorly known despite the threats to the persistence of this group of species. In grasslands, prior vole (Microtus californicus) exclusion created long-lasting gains in bush lupine abundance, mediated through the seedbank, and was associated with increased snail numbers (10×) compared to control plots where mammals were never excluded. Similar plots in dune habitat showed no difference in snail numbers due to previous mammal exclusion. We tested whether increased competition for food, increased predation, and/or lower desiccation explained the decline in snail numbers in plots with reduced lupine cover. Tethering experiments supported the hypothesis that voles can have long-lasting impacts as ecosystem engineers, reducing woody lupine habitat required for successful aestivation by snails. These results add to a growing list of studies that have found that non-trophic interactions can be limiting to invertebrate consumers.     

Molecular dating and biogeography of the early placental mammal radiation

The timing and phylogenetic hierarchy of early placental mammal divergences was determined based on combined DNA sequence analysis of 18 gene segments (9779 bp) from 64 species. Using rooted and unrooted phylogenies derived from distinct theoretical approaches, strong support for the divergence of four principal clades of eutherian mammals was achieved. Minimum divergence dates of the earliest nodes in the placental mammal phylogeny were estimated with a quartet-based maximum-likelihood method that accommodates rate variation among lineages using conservative fossil calibrations from nine different nodes in the eutherian tree. These minimum estimates resolve the earliest placental mammal divergence nodes at periods between 64 and 104 million years ago, in essentially every case predating the Cretaceous-Tertiary (K-T) boundary. The pattern and timing of these divergences allow a geographic interpretation of the primary branching events in eutherian history, likely originating in the southern supercontinent Gondwanaland coincident with its breakup into Africa and South America 95-105 million years ago. We propose an integrated genomic, paleontological, and biogeographic hypothesis to account for these earliest splits on the placental mammal family tree and address current discrepancies between fossil and molecular evidence.     

Demography of fluctuating vole populations: Phase homogeneity of demographic variables

Most research on fluctuations of arvicoline rodents has focused on changes in demographic variables across phases. Here, we examined whether demographic variables varied within a phase (trough, increase, and decline) across 30 fluctuations of Microtus ochrogaster and 14 fluctuations of Microtus pennsylvanicus over 25 years. For each species, we tested for phase homogeneity (i.e., values of demographic variables were invariant across all fluctuations within a given phase) for the following demographic variables: monthly survival (total, adult, young), proportion of reproductively active adult males and females, proportion of young, and proportion of immigrants. We found phase homogeneity for 96.7% of the 582 phase/fluctutation data sets for the seven variables, in the three phases of across all fluctuations in the three habitats for M. ochrogaster and 98.0% of 254 of those for M. pennsylvanicus in two habitats. We conclude that for each of these two species demographic variables are relatively invariant both within a phase and across fluctuations.