Rodent Assemblages Research Articles

Regional and local determinants of rodent assemblages in agroecosystems of the Argentine Pampas

Regional and local determinants of rodent assemblages in agroecosystems of the Argentine Pampas

Preliminary study of the rodent assemblages of Goda Buticha: New insights on Late Quaternary environmental and cultural changes in southeastern Ethiopia

Given its proximity to the Strait of Bab el Mandeb and the Red Sea, the Horn of Africa is particularly important for understanding human and faunal migration events to and from Africa. Towards the end of the Pleistocene, the Middle/Later Stone Age (MSA/LSA) transition represents a critical step in human cultural evolution. However, in the Horn of Africa, the environmental conditions associated with this transition remain poorly understood. The Goda Buticha (Buticha cave) sequence, located in southeastern Ethiopia, and dated from ca. 63 ka cal BP to ca. 1 ka cal BP, provides a rare opportunity to examine the environmental contexts associated with major cultural sequences documented in the region during this time period. A preliminary analysis of the rich microvertebrate (and especially rodent) remains recovered from the levels dated between 43 and 4 ka BP identified fourteen different rodent genera, including two species that are locally extinct in southeastern Ethiopia today. While the taphonomic signature is similar throughout the sequence, indicating an in situ accumulation by an owl without major perturbation, the palaeoecological analysis showed environmental change through time, characterized by open-dry setting during the Late Pleistocene, shifting to wetter and more wooded conditions heading to the Holocene. These results are generally consistent with other diverse records which include the large mammals, speleothems and lake basins records, and allow a better understanding of the dynamics of environmental contexts associated with observed cultural change and continuity in eastern Africa from the Late Pleistocene to Late Holocene.

First faunal insights from biozone Db (middle Miocene, middle Aragonian) of the Madrid Basin (Spain)

Palaeontological excavations following public works around the Manzanares River in the metropolitan area of Madrid yielded new small mammal fossil remains from two locations. We present here a description of their rodent assemblages, and a biostratigraphical and palaeoecological context of them. A comparison of these levels to the contemporaneous fossil localities of the Calatayud-Montalban Basin and to other middle Aragonian sites from Madrid is also shown. A total of 371 dental elements have been studied from the five levels of the two locations (Puente de Praga site and Madrid Rio2 site). The rodent associations from the five new levels are similar and comprise eight taxa: Megacricetodon primitivus, Megacricetodon vandermeuleni, Democricetodon moralesi, Democricetodon sp., Armantomys aragonensis, Microdyromys koenigswaldi, Pseudodryomys ibericus and Heteroxerus rubricati. It represents a low equitable rodent community characterized by the predominance of the genus Megacricetodon and a poorly-represented fauna of glirids and sciurids. The fossil association and its biostratigraphical markers indicate a correlation of the levels to the upper part of biozone Db, this being the first time that the rodent assemblages of this biozone are described in the Madrid Basin. Based on the rodent content we suggest more humid or/and more closed environments in biozone Db than in biozones Dc and Dd. The Calatayud-Montalban record shows more diverse rodent assemblages in biozone Db, with taxa not recorded in Madrid that are indicative of more humid or structured environments. Therefore, the Madrid associations would represent dryer or/and more open environments than the Calatayud-Montalban associations.

Middle to Late Pleistocene environmental and climatic reconstruction of the human occurrence at Grotta Maggiore di San Bernardino (Vicenza, Italy) through the small-mammal assemblage

Grotta Maggiore di San Bernardino, located at an altitude of 135 m a.s.l. in the Berici Hills in northeastern Italy, is an archaeological site with a discontinuous sedimentary sequence dating from Marine Isotope Stage 7 (MIS 7) to MIS 3. In this paper we present for the first time a palaeoenvironmental and palaeoclimatic reconstruction of the sequence based on small-mammal (insectivore, bat and rodent) assemblages. Coupled with biochronological data and absolute dating together with previous studies on large mammals, birds and other studies on small mammals and pollen from comparable time-spans in Italy, the results enable us clearly to identify distinct climatic periods: the end of MIS 7 (7c to 7a) in units VIII-VII, MIS 5d in unit V, and probably MIS 5b in unit IV and an indeterminate MIS 3 interstadial in units III-II. Finally, the study shows that the early Middle Palaeolithic human occupation in Italy occurs during mild and temperate sub-stages of MIS 7 and that human groups with the same techno-cultural background (Mousterian) were well adapted to the changing environmental and climatic conditions of the Middle to Late Pleistocene in this part of southern Europe.

Roedores sigmodontíneos (Mammalia, Rodentia, Cricetidae) holocênicos do Rio Grande do Sul, Brasil – o Sítio RS-TQ-58: Afonso Garivaldino Rodrigues

We present the sigmodontine assemblage from lower and middle Holocene recorded in the archaeological site RS-TQ-58: Afonso Garivaldino Rodrigues (County of Brochier, State of Rio Grande do Sul). A total of 16 species are detected from the study of 572 specimens, about half of which belonging to the tribe Akodontini. The assemblage recorded include species which typically inhabit open areas (e.g. Calomys sp., Gyldenstolpia sp., Kunsia tomentosus) and also several considered as forest dewellers (e.g. Delomys sp., Juliomys sp., Sooretamys angouya). Necromys obscurus, a sigmodontine today restricted to Central Argentina and Southern Uruguay, is abundantly recorded in Garivaldino and reported for the first time to the Quaternary from Brazil. Thaptomys nigrita and Wilfredomys oenax have in Garivaldino their first records to the Holocene from Rio Grande do Sul State. Compared to the recent assemblage of sigmodontine rodents recorded in Rio Grande do Sul, Pseudoryzomys simplex, K. tomentosus, N. obscurus and Gyldenstolpia sp. became regionally extinct. The sigmodontine assemblage detected in Garivaldino is richest than a previously studied one from Pilger site. The evidence of both sites reflects changes in the species composition, which can be linked with a progressive transformation of the general landscape from mostly open grasslands to forests.

Les Cases de la Valenciana, a new early Miocene small-mammal locality from the Vallès-Penedès Basin (Catalonia, Spain)

The Valles-Penedes Basin (Catalonia, Spain) is classical area for the study of Miocene land mammal faunas. Nevertheless, the early Miocene part of the record has deserved little attention as compared to younger intervals. Most notably, the small mammals of this age have not been described in detail, consequently hampering the correlation of the Valles-Penedes record with other chronological schemes. In this work we describe the rich and diverse small mammal fauna from Les Cases de la Valenciana site (Gelida, Alt Penedès) which includes marsupials, eulipotyphlans, lagomorphs and rodents. On the basis of the presence of the cricetids Megacricetodon and Democricetodon this site is correlated with European Neogene zone MN4, yielding an age of 17–16 Ma. However, the rodent assemblage is comparable to that of chronologically close localities of the Calatayud-Montalbán Basin (Aragon, Spain), indicating that the same biochronological scheme can be applied to both areas. In this way, the coexistence of the eomyids Ligerimys ellipticus and Ligerimys florancei coupled with the presence of Megacricetodon primitivus indicates a correlation with local biozone Ca of the Calatayud-Montalban Basin, ranging from 16.3 to 16 Ma. Finally, the correlation of other early Miocene sites of the Valles-Penedes Basin is discussed and refined.

First report of rodents from the late Hemphillian (late Miocene) Zwiebel Channel and a revised late Neogene biostratigraphy/biochronology of the Sand Draw area of Nebraska

A new late Hemphillian (late Miocene) rodent assemblage is reported from Zwiebel Channel, a channel cut into underlying Ash Hollow Miocene sediments along Sand Draw, Brown County, Nebraska. This locality extends the temporal range of rodent history in the Sand Draw area. A new biostratigraphic hypothesis proposes that previously described assemblages with Ogmodontomys are older than those with Ophiomys, as is the case in the Meade Basin of southwestern Kansas. Consequently, two Pliocene temporal zones are recognised. Based on a phylogenetic analysis of Ophiomys, rodent biostratigraphy, and paleomagnetic profiles, Sand Draw assemblages with Ogmodontomys are considered to have been deposited about 3.0–2.8 Ma, while those with Ophiomys were laid down between about 2.8–2.5 Ma. The 1.6 Ma date previously suggested for Ophiomys parvus from Froman Ferry, Idaho is probably too young; it is more likely that O. parvus became extinct in Idaho prior to the North American Microtus immigration event at about 2.0 Ma, inhabiting the Snake River basin until around 2.2 Ma.

Morphometric patterns in assemblages of Cricetid rodents from the Central and Western Cordilleras of Colombia

The mechanisms that mediate the formation and coexistence of species assemblages have been a historical issue in evolutionary ecology, raising the question of whether these assemblages are shaped at random or are influenced by biotic and abiotic processes. An increasingly popular hypothesis points out that certain patterns or rules determine coexistence patterns within assemblages at a regional or continental scale. Thus, morphological and ecological similarities could influence the degree and intensity of competition between species. Considering the morphology of organisms within an environmental framework, we could assess the morphology and understand the ecological role of a given species within the assemblage. This study assesses the similarities and differences of Andean rodents within local assemblages through a Principal Component Analysis (PCA), using craniodental characters of these species to establish whether the relationships between morphometry and coexistence provide evidence to explain assemblage structure patterns. We measured rodent specimens deposited in the Coleccion Teriologica of the University of Antioquia, collected from the Western and Central cordilleras of Colombia. We recorded 15 craniodental variables from all specimens, which were analyzed with a PCA to search for a general organization pattern within assemblages. Afterwards, we plotted the scores for principal components 1 and 2 to evidence the separation or clustering of specimens in an Euclidean space. We recorded 424 specimens from 10 genera and 18 species of the family Cricetidae, with the genera Nephelomys and Thomasomys showing the largest number of specimens. In the overall PCA, the first three components account for 85.1 % of the variation, with 63.9 % for PC1. The variables with the greatest contributions to PC1 were APZ, AA and AFM; to PC2, LFI, APZ and AFM; and to PC3, LFI, LO and LHM. We detected some overlapping and scattering patterns among species at the morphospace defined by PC1 and PC2. We recovered an arrangement of species that shows differences in size and shape between them (as a function of their morphology), as evidenced in the scatter plots for the regional and local analyses. Besides, we did not find a general pattern for the load of variables, although some of these accounted for a larger part of the variation in the overall and local analyses (APZ, AFM, LFI, LHM and AR), indicating the segregation among species. Although the local analyses revealed a similar pattern with these loads changing from site to site, five variables account for the largest variation, what we interpret as a key role to determine the morphometric and/or ecological segregation among species. We believe this first approximation shows the value of ecomorphological studies in understanding patterns of diversity and geographic replacement of species; these patterns should be integrated with analyses of ecological aspects to understand the coexistence of species within local assemblages.

Impact of global climate in the diversity patterns of middle Miocene rodents from the Madrid Basin (Spain)

Remarkable palaeoclimatic global changes have been recorded worldwide during the middle Miocene. The Miocene Climatic Optimum (~16.3 to ~15Ma), one of the warmest phases since the Eocene, was followed by the stepwise cooling trend of the Middle Miocene Climate Transition (~15 to ~13.7Ma). The entry into an Earth “Ice-house” climate state took place at the end of the latter (~13.76Ma) marked by one of the major cooling steps in middle Miocene climate recorded at a global scale (Mi3b event). The Madrid Basin, which is part of one of the main Cenozoic basins of the Iberian Peninsula, contains a well-represented small-mammal record from the lower middle Miocene to the upper middle Miocene (middle and upper Aragonian, ~15.9 to 12.8Ma), being an appropriate region to check how these climatic phases influenced the distribution of the mammalian faunas on the center of the Iberian Peninsula. Values of species richness, equitability and heterogeneity of rodents have been calculated for 25 localities of the Madrid Basin and compared to detailed climate isotope records from the marine realm (ODP Site 1146 from the South China Sea and the Mediterranean record of the Ras Il Pellegrin section on the Maltese Islands) and with palaeoprecipitation curves for southwest Europe (Calatayud-Montalbán Basin). The results show that the rodent community during the middle and upper Aragonian in the Madrid Basin was subject to the changing climate conditions imposed in the course of the middle Miocene. The palaeoecological curves witness periods of disturbance of the community during changing climate conditions (marked by important drops in equitability and, in some cases, gradual decreases in heterogeneity and species richness), followed by periods showing a recovery of the community and adaptation to the new climate circumstances (represented by more evenly distributed and diverse assemblages). The effects of the Miocene Climate Optimum and of three Mi-events (Mi2b, Mi3a and Mi3b) have been related to changes in the small-mammal community. Between ~15.8 and 15.3Ma, the likely extreme environment (high temperature and low precipitation) of part of the Miocene Climate Optimum may have imposed severe constraints on the fauna, resulting in a community with low values of equitability, heterogeneity and a decreasing number of species. The transition of the Miocene Climate Optimum to the Middle Miocene Climate Transition, reflected by the Mi2b event, has also procured a destabilization of the rodent assemblages, as an important drop in equitability is recorded between ~15 and 14.6Ma. In this interval, the drop in temperature and increase in rainfall derived from the Middle Miocene Climate Transition promote the southwards migration of northern invaders, leading to an increase in species richness in the Madrid Basin. Starting around 14.4Ma, the onset of a progressive drop in the rodent equitability and heterogeneity, which also coincides with a major stratigraphic discordance in the basin, is related to the first cooling step of the Middle Miocene Climate Transition (Mi3a event). Finally, the major cooling step in middle Miocene climate recorded at a global scale (Mi3b event) is poorly reflected in the palaeoecological curves. However, the taxonomical study of the rodent faunas of that interval (biozone E) has shown turnover rates and morphometric changes that indicate that this period represents one of the most variable in assemblage composition within the Aragonian. Although the Mi3b event has been correlated for a long time to the substitution of the early-middle Aragonian fauna by a late Aragonian community (E–F boundary), the study of the rodent assemblages of the Madrid Basin may point out that small changes in the small-mammal community started before (within biozone E).

Updated biochronology of the Madrid Basin: species distribution and implications for the Middle Miocene rodent faunas of Spain

The works carried out in the Madrid area during the last fifteen years have yielded almost twenty new localities including small-mammals. A taxonomical description of the rodent fauna of the new sites and a revision of those previously published has enabled us to present an updated biostratigraphy and biochronology for the middle and upper Aragonian of the Madrid Basin. Seven local biozones are recognised: Db, Dc, Dd, E, F, G1 and G2. The rodent assemblage of biozone Db is here described for the first time in Madrid. The new finds have also filled poorly-known parts of biozones Dc, Dd, E and F, making now the rodent assemblages of biozones Dc and E from Madrid one of the most complete and best-represented records. Considering the faunal variability in biozone G1 in the Madrid Basin, we propose a new definition for it. The comparison of the rodent assemblages between the Madrid and Calatayud-Montalbán basins points out that both share several similarities in their taxonomical distributions, although with less diverse faunas in Madrid. A relative impoverishment in taxa of complicated dental pattern in Madrid could be interpreted as due to differences in the local environment with Calatayud.

Rodent consumption by hunter-gatherers in north Patagonian Andean forests (Argentina): Insights from the small vertebrate taphonomic analysis of two late Holocene archaeological sites

Modern taphonomic studies carried out upon small rodent assemblages from arid Patagonia demonstrates rodent consumption in several late Holocene archaeological sites. Conversely, very little is known about the exploitation of these small mammals by hunter-gatherers that inhabited the North Patagonia Andean forest (NPAF). Human occupation in forests dates back to late Pleistocene – early Holocene but its use was non-existent until the late Holocene (1700years BP), when a more recurrent and/or more extended stays in the forest took place. In order to advance in the understanding of the subsistence strategies displayed by hunter-gatherers in Patagonian forests, human involvement in the accumulation of rodent bones was evaluated from two archaeological sites located in the NPAF: Paredón Lanfré (SW Río Negro) and Risco de Azócar 1 (NW Chubut). The taphonomic analysis included the estimation of the MNE and MNI, the relative abundance, and the representation of skeletal elements. Heat alteration of bone surface and the presence of cut marks and digestion traces were also evaluated. Caviomorpha rodents dominate the small vertebrate's assemblages. Thermal alteration and differential representation of skeletal pieces –over-representation of skulls and distal elements of the limbs- suggest that human consumption was the main cause of accumulation of these rodents. The consumed species were Galea leucoblephara, Microcavia australis, Ctenomys haigi and possibly also C. sociabilis. We concluded that this consumption seems to reflect the exploitation of low ranked prey individuals in a low productive environment.

What bite marks can tell us: Use of on-fruit tooth impressions to study seed consumer identity and consumption patterns within a rodent assemblage

Rodents have a highly specialized dentition, and incisor dimensions are very characteristic within each group. In this study we field-tested a rarely-used methodology – using marks left by rodent incisors in fruits and seeds to identify them. The width of the incisors marks made in Plasticine™ blocks using skulls from museum collections, were compared with the marks left on field-collected fruits and seeds. We confirmed the existence of allometric relationship between incisors width and body size. Furthermore larger and harder fruits showed larger bite marks compared with smaller and soft fruits/seeds, indicating the importance of fruit size and hardness in rodent food-plant selection. Based on tooth width measurements, the results also showed that smaller fruits/seeds are used by fewer rodent species, in comparison to fruits of larger size, these being more likely to be consumed and/or predated. Due to an overlap in body size between species, the method did not provide precise identifications of the rodent species consuming particular items, although it does reduce the likely suite of species responsible. However, when used in conjunction with the more commonly deployed tools, this method is highly viable due to easy use and low cost. Future studies using bite marks images and a greater range of morphological features could increase the precision of this technique.

Late Oligocene caviomorph rodents from Contamana, Peruvian Amazonia

AbstractThe Deseadan South American Land Mammal Age (late Early Oligocene – Late Oligocene) attests to a time of great diversification in the caviomorph rodent fossil record. Nevertheless, Deseadan rodent‐bearing localities in Neotropical lowlands are few and poorly known. Here we describe the rodent assemblages from two Late Oligocene localities, near Contamana, Loreto, Peru. Seven taxa are new to science: Palaeosteiromys amazonensis gen. et sp. nov., Plesiosteiromys newelli gen. et sp. nov., Loretomys minutus gen. et sp. nov., Scleromys praecursor sp. nov, Ucayalimys crassidens gen. et sp. nov., Chambiramys sylvaticus gen. et sp. nov. and Chambiramys shipiborum gen. et sp. nov. These rodent faunas show that caviomorphs were relatively diverse in Peruvian Amazonia during the Late Oligocene, with the co‐occurrence of at least three extant superfamilies: Erethizontoidea, Octodontoidea and Chinchilloidea. Additionally, they mark the earliest known occurrences of Scleromys, of a small erethizontid closely related to Microsteiromys and of an adelphomyine closely reminiscent of Ricardomys (all taxa previously restricted to Miocene localities thus far). They also document a form potentially related to Eosallamys (previously known from around the Eocene–Oligocene transition at Santa Rosa in Peruvian Amazonia). Finally, the geographical range of Adelphomyinae and of Deseadomys is widely expanded to the lower latitudes of South America for the Deseadan interval. The latter elements, in addition to the record of a very primitive species of Scleromys, suggest the absence of palaeogeographical and palaeoenvironmental barriers within the southern cone of South America before the Oligocene–Miocene transition.

Influence of vegetation type and season on rodent assemblage in a Mexican temperate forest mosaic

Knowing the factors that influence abundance, distribution and species richness is key to establish local conservation strategies. We evaluated the influence of vegetation type (pine, oak-alder-forest and grassland) and (dry, wet) season on the assemblage rodent in a mosaic of temperate forest in Mexico. The completeness of the inventory was evaluated by nonparametric estimators ACE and Jackknife. We use a generalized linear model to evaluate the effect of vegetation type, season and interaction (vegetation type*season) on the richness and abundance of rodents. The effect of factors and their interaction on the abundance of each species were evaluated with two-way analysis of variance with rank transformations. To analyze changes in the assembly structure we used rank-curves abundances and ANCOVA to assess differences in dominances/evenness of species. We found that rodents were more abundant in the pine forest and during the dry season, but the interaction between oak-alder forest and the dry season also favored abundance. At species level, Peromyscus melanotis was abundant in the pine forest and Reithrodontomys fulvescens in the oak-alder-forest. Between seasons, only the abundance of P. maniculatu s was higher in the dry season than the wet season. The results show that mosaics with trees are of crucial importance for rodent’s conservation during the dry seasons.

Insights on the host associations and geographic distribution of Hymenolepis folkertsi (Cestoda: Hymenolepididae) among rodents across temperate latitudes of North America.

Synoptic data and an understanding of helminth parasite diversity among diverse rodent assemblages across temperate latitudes of North America remain remarkably incomplete. Renewed attention to comprehensive survey and inventory to establish the structure of biodiverse faunas is essential in providing indicators and proxies for identifying the outcomes of accelerating change linked to climate warming and anthropogenic forcing. Subsequent to the description of Hymenolepis folkertsi in the oldfield mouse, Peromyscus polionotus, additional specimens of hymenolepidids were collected or discovered in archived museum repositories from multiple species of deer mice (Peromyscus maniculatus, Peromyscus leucopus), the golden mouse (Ochrotomys nuttalli), chipmunks (Tamias striatus, Tamias amoenus), the 13-lined ground squirrel (Ictidomys tridecemlineatus), and tree squirrels (Sciurus carolinensis, Sciurus niger) from disjunct localities in the USA spanning southern Georgia, Virginia, Pennsylvania, Connecticut, the Upper Peninsula of Michigan, Wisconsin, and central Idaho. Specimens were largely consistent morphologically with the original description of H. folkertsi. Initial DNA sequence data, from a portion of the mitochondrial NADH dehydrogenase subunit 1, demonstrated intraspecific variation among three apparently geographically isolated populations attributed to H. folkertsi (uncorrected genetic distances of 2.7 % (Idaho and Michigan), 2.4 % (Virginia + Pennsylvania and Michigan), and 1.89 % (VA + PA and ID). Geography rather than host association explains the distribution and occurrence of H. folkertsi, and host colonization among deer mice, chipmunks, and other sciurids within regional sites is indicated. Genetic divergence revealed across localities for H. folkertsi suggests historically isolated populations, consistent with extended evolutionary and biogeographic trajectories among hymenolepidids and species of Peromyscus and Tamias in North America. Field inventory, that revealed these parasite populations, substantially alters our understanding of the distribution of diversity and provides insights about the nature of the complex relationships that serve to determine cestode faunas in rodents.

Intercontinental-wide consequences of compromise-breaking adaptations: the case of desert rodents

Desert rodent assemblages from around the world provide convergent, but independent crucibles for testing theory and deducing general ecological principles. The heteromyid rodents of North America and the gerbils of the Middle East and their predators provide such an example. Both sets of rodents face predation from owls and vipers, but the North American species possess unique traits that may represent macroevolutionary breakthroughs: rattlesnakes have infra-red sensitive sensory pits, and heteromyids have cheek pouches. To test their significance, we brought together two gerbils (Middle East), two heteromyid rodents (a kangaroo rat and a pocket mouse; North America) in a common setting (a vivarium in the Negev Desert), and quantified the “opinions” of the rodents towards the North American sidewinder rattlesnake and the Middle Eastern Saharan horned viper and the foraging behavior of each in the face of these snake predators plus owl predators. Gerbils are fairly evenly matched in their anti-predator abilities, while the heteromyids differ widely, and these seem to match well with and may determine the types of mechanisms of species coexistence that operate in the communities of each continent. Evolutionary history, macroevolutionary traits, and risk management therefore combine to determine the characteristics of the organisms and the organization of their communities.

Stronger effect of gastropods than rodents on seedling establishment, irrespective of exotic or native plant species origin

Experimental evidence about how generalist consumers affect exotic plant invasions is equivocal, but most tests have been limited to few plant species, single herbivore guilds, and single locations. Using a seed‐addition experiment, we studied effects of gastropods and rodents on recruitment success of 37 exotic and 37 native plant species affiliated to three different functional groups (i.e. grasses, legumes and non‐legume herbs). We replicated our seed addition x herbivore exclusion experiment at multiple grassland sites, located within a few km of each other in two regions, coastal central California (USA) and southern Saxony–Anhalt (Germany). The two study regions differed in climate, land‐use, invasion history and species pools which allowed us to disentangle general from context‐specific effects. In both regions, herbivory by gastropods had a stronger impact on the proportion of recruited seedlings and the proportion of recruited species than rodent herbivory, but this effect was much more pronounced in California than in Germany. Especially, seedling recruitment of non‐legume herbs and legumes suffered from gastropod herbivory. Contrastingly, the effect of rodents was negative at the German sites and positive at the Californian sites, likely driven by context‐specific differences in the rodent assemblages. Across both study regions, exotics had higher seedling recruitment than natives, indicating that higher recruitment success constitutes an inherent feature of exotic species. After two years, more exotic than native species established at grassland sites in California while the opposite was true for the German grassland sites. Consistently across regions, native and exotic species did, however, not differ in their response to herbivory, suggesting that generalist consumers suppress recruitment and colonization of plant species irrespective of their origin. Our results demonstrate the importance of a multi‐species, multi‐site approach to separate general responses of exotic and native plants to generalist herbivory from local, regional or species‐specific peculiarities.

Primary seed dispersal by a sigmodontine rodent assemblage in a Peruvian montane forest

Abstract:We examined quantity and quality components of primary seed dispersal for an assemblage of sigmodontine rodents in a high-elevation montane tropical forest in Peru. We collected faecal samples from 134 individuals belonging to seven rodent species from the subfamily Sigmodontinae (Cricetidae) over a 2-y period. We conducted seed viability tests for seeds found in faecal samples. We identified seeds from eight plant families (Bromeliaceae, Annonaceae, Brassicaceae, Ericaceae, Melastomatacae, Myrtaceae, Rosaceae, Solanaceae), nine genera and 13 morphospecies. The most abundant seeds belonged toGaultheriasp. 1 (46% of total) andMiconiasp. 1 (31% of total), while the most viable seeds belonged toGreigiasp. (84% viability) andGuatteriasp. (80% viability). We utilized relative rodent abundance, seed species diversity, seed abundance and seed viability per rodent species to calculate an index of rodent disperser effectiveness, and found thatThomasomys kalinowskiiwas the most effective disperser, followed byAkodon torques,Calomys sorellus,Thomasomys oreas,Oligoryzomys andinusandMicroryzomys minutus. Plant genera dispersed by sigmodontine rodents overlapped more with bird- and terrestrial-mammal-dispersed plants than with bat-dispersed plants. Future neotropical seed dispersal studies should consider small rodents as potential seed-dispersers, especially in tropical habitats where small-seeded, berry-forming shrubs and trees are present.

Early Eocene (Wasatchian) rodent assemblages from the Washakie Basin, Wyoming

Rodent assemblages are described from two early Eocene (Wasatchian North American Land Mammal Age; Graybullian subage) localities from the Main Body of the Wasatch Formation in the Washakie Basin, Wyoming. One locality (UCMP V71237) represents a catastrophic death assemblage and the other (UCMP V71238) is a channel lag which immediately overlies it. Quarrying and screen-washing at these localities has resulted in the recovery of 81 specimens from V71237 and 224 specimens from V71238 and comprising a uniquely rich, stratigraphically controlled sample. The rodent fauna from these localities include Paramys copei, P. taurus, Lophiparamys murinus, Microparamys hunterae, Tuscahomys ctenodactylops, and Knightomys cf. K. minor. These specimens provide substantial new morphological data for the previously poorly-known M. hunterae, T. ctenodactylops, and L. murinus. Comparison of relative abundances demonstrates that T. ctenodactylops is the most common in both localities, but that the smaller bodied species M. hunterae and Knightomys cf. K. minor are much rarer in the lag deposit.

Palaeoecological implications of rodents as proxies for the Late Pleistocene–Holocene environmental and climatic changes in northeastern Iberia

Rodents are among the most useful proxies for reconstructing the ecology and environment of the Quaternary. The present paper focuses on a series of fossil rodent assemblages from northeastern Iberia of the Late Pleistocene (ca. 128–11.7 ka BP) and the beginning of the Holocene (<11.7 ka BP). Descriptive and multivariate statistical methods have been applied to expand what is known about the species involved and their palaeoecological implications. The results show the importance of the three predominant species: Microtus arvalis, Microtus agrestis and Apodemus sylvaticus. A transition in the ecological conditions is shown in the studied area during the course of this interval: from open environments and cooler climatic conditions to more forested landscapes and temperate conditions. The beginning of the Late Pleistocene and the Holocene share similarities, and both differ clearly from the end of the Late Pleistocene, showing the singular nature of the environmental conditions of Marine Isotope Stage 2 in the northeastern sector of the Iberian Peninsula.