Compensation of rodent pests after removal: control of two rat species in an irrigated farming system in the Red River Delta, Vietnam

Rodent pests have a strong capacity to recover rapidly from imposed reductions in abundance, but it is unclear how populations compensate to removal when farmers apply rodent control. The response of two rat species to rodent control was monitored using regular live-trapping in an irrigated lowland mixed rice agroecosystem. Rice field rats, Rattus argentiventer (52% of rodent captures), and lesser rice field rats, Rattus losea (29%), were removed using trap-barrier systems (TBS) at two sites while rice crops were present. The TBS was a plastic fence that enclosed a small field planted 3 weeks prior to the surrounding fields and set with multiple-capture cage-traps to capture rats that were attracted to the early-planted crop. Demographic responses of rats were compared to two untreated sites. There was a reduction in abundance of rodents on treated sites relative to untreated sites during the summer rice crop (by 45% and 28% for R. argentiventer and R. losea, respectively) an increase in abundance during the winter season (31% and 69%), and a mixed response during the spring rice crop (39% decrease and 41% increase). There was an increase in the proportion of juveniles captured on treated sites relative to untreated sites post-treatment (148% and 158%) and the body mass was lower on treated sites post-treatment (males: 13% and 41%; females: 22% and 22%). Older, larger animals were removed by the TBS and the rodent populations were compensating through high recruitment of young and high immigration into treated sites. No clear patterns were observed in the occurrence of adult breeding females for either R. argentiventer or R. losea. Rodent management, should therefore, occur over large areas (> 100 ha) to reduce the chance of reinvasion.     

Population dynamics of Rattus argentiventer, Rattus losea, and Rattus rattus inhabiting a mixed-farming system in the Red River Delta, Vietnam

Rodent pests cause significant damage to lowland irrigated rice crops in the Red River Delta of northern Vietnam. Data from a 4-year study were examined to look at the population dynamics of the ricefield rat, Rattus argentiventer (representing 50% of captures), the lesser ricefield rat, Rattus losea (30% of captures), and the black rat, Rattus rattus complex (9% of captures) that inhabit the irrigated mixed-cropping system. We tested the hypothesis that these rodent species were breeding in response to the availability of high-quality food provided by crops rather than in response to rainfall. The abundance of rodents fluctuated annually, with a main peak following the spring rice crop, and a secondary peak following the summer rice crop. There was a strong relationship between the monthly abundance of rats and rainfall, but a weak relationship between monthly rates of increase and rainfall. There were distinct peaks in breeding activity during the reproductive stages of the rice crops suggesting that changes in crop stages were more important than rainfall in this seasonal, but irrigated agroecosystem. The modal litter size for R. argentiventer was 8 (mean of 8.67±0.20 SE, range 2–16), where the mode for R. losea, was 7 (mean of 7.32±0.15 SE, range 3–14). Management of these species needs to be conducted prior to the onset of the main breeding seasons.     

The susceptibility of Apodemus agrarius and Rattus losea to the anticoagulant rodenticide,flocoumafen

Flocoumafen had good rodenticidal action against Apodemus agrarius and Rattus losea. The acute oral LD₅₀ for male A. agrarius and R. losea was 1·22 mg kg⁻¹ and 1·36 mg kg⁻¹ respectively. Flocoumafen bait was more toxic to R. losea than to A. agrarius. At bait concentrations of 0·002–0·005%, flocoumafen had a single-feed potency with mortalities of 90–100% for R. losea and 77·8–100% for A. agrarius. Experimental baits prepared using the manufacturing 0·5% master mix of flocoumafen were palatable to both species.     

Schistosoma incognitum from Cikurai,West Java,Indonesia

Schistosoma incognitum is reported for the first time from West Java, Indonesia where 84% of ricefield rats, Rattus argentiventer, were infected. Radix auricularia rubiginosa snails were intermediate hosts. The adult stage of the Javanese strain of S. incognitum and lesions in naturally-infected rodents are described. Rattus exulans, Rattus norvegicus and Mus musculus were experimentally infected. Epizootiology is similar to that described in other countries.     

The prevalence and genomic characteristics of hepatitis E virus in murine rodents and house shrews from several regions in China

Background

Urban rodents and house shrews are closely correlated in terms of location with humans and can transmit many pathogens to them. Hepatitis E has been confirmed to be a zoonotic disease. However, the zoonotic potential of rat HEV is still unclear. The aim of this study was to determine the prevalence and genomic characteristics of hepatitis E virus (HEV) in rodents and house shrews.

Results

We collected a total of 788 animals from four provinces in China. From the 614 collected murine rodents, 20.19% of the liver tissue samples and 45.76% of the fecal samples were positive for HEV. From the 174 house shrews (Suncus murinus), 5.17% fecal samples and 0.57% liver tissue samples were positive for HEV. All of the HEV sequences obtained in this study belonged to Orthohepevirus C1. However, we observed a lower percentage of identity in the ORF3 region upon comparing the amino acid sequences between Rattus norvegicus and Rattus losea. HEV derived from house shrews shared a high percentage of identity with rat HEV. Notably, the first near full-length of the HEV genome from Rattus losea is described in our study, and we also report the first near full-length rat HEV genomes in Rattus norvegicus from China.

Conclusion

HEV is prevalent among the three common species of murine rodents (Rattus. norvegicus, Rattus. tanezumi, and Rattus. losea) in China. HEV sequences detected from house shrews were similar to rat HEV sequences. The high identity of HEV from murine rodents and house shrews suggested that HEV can spread among different animal species.

     

Focus: Zoonotic Disease: Prevalence and Diversity of the Streptobacillus Rat-bite Fever Agent,in Three Invasive,Commensal Rattus Species from South Africa

Rat-bite fever is an over-looked, global zoonotic disease that has a mortality rate of up to 13%, if untreated. Historically, this rat-borne disease has been attributed to one of two causative agents, Streptobacillus moniliformis or Spirillum minus. Given the confirmed presence of multiple invasive Rattus host species, high rat densities in urban, informal human settlements and increasing reports of rat bites in South Africa, we undertook a retrospective assessment of Streptobacillus in rats sampled from 16 urban sites, in Gauteng, the smallest but most populous Province in South Africa. Using a multi-gene PCR-sequencing approach, we confirmed Streptobacillus presence in 50.9% of oral swabs from three rat species and the presence of two Streptobacillus species, viz. S. moniliformis and S. notomytis. The two members of the cryptic Rattus rattus species complex (R. rattus and R. tanezumi), which are morphologically indistinguishable from each other, had markedly different colonization rates. Whereas 48.6% of rats from this species complex were Streptobacillus-positive, only 32.3% of Rattus tanezumi were positive compared to 61.5% R. rattus. Rattus norvegicus had an intermediate prevalence of 55.6%. Phylogenetic analysis of four gene regions (16S rRNA, gyrB, groEL, recA) identified two discrete lineages; S. moniliformis occurred exclusively in R. norvegicus, and S. notomytis was restricted to the two members of the R. rattus species complex; this represents the first report of Streptobacillus in R. tanezumi. These results highlight a largely overlooked zoonotic threat posed by invasive rats and confirm the presence of two discrete and potentially host-specific Streptobacillus lineages in South Africa.     

Large-scale rodent control reduces pre- and post-dispersal seed predation of the endangered Hawaiian lobeliad, Cyanea superba subsp. superba (Campanulaceae)

Large-scale rodent control can help to manage endangered species that are vulnerable to invasive rodent consumption. A 26?ha rodent snap-trap grid was installed in montane forest on Oahu Island, Hawaii, in order to protect endangered snails and plants. To assess the effectiveness of this trapping operation in reducing fruit consumption and seed predation of the endangered Hawaiian lobeliad, Cyanea superba subsp. superba, pre- and post-dispersal C. superba fruit consumption were monitored for 36 plants at the site with rodent control (Kahanahaiki) and 42 plants at an adjacent site without rodent control (Pahole). Over 47?% of all monitored fruit were eaten on the plants at Pahole compared to 4?% at Kahanahaiki. Images captured using motion-sensing cameras suggest that black rats (Rattus rattus) were the only pre-dispersal fruit consumers. To quantify post-dispersal fruit consumption, and to identify the culprit frugivore(s), mature fruit were placed in tracking tunnels positioned on the forest floor and checked daily. At Pahole, all of the fruit were consumed by rats compared to 29?% at Kahanahaiki. Lastly, to determine if rodents from the sites were predators or dispersers of C. superba seed, fruit were fed to captive black rats and house mice (Mus musculus). Black rats consumed entire fruit, killing all the seed, while mice did little damage to the fruit and seed. Therefore, large-scale rat trapping can directly benefit the reproduction of C. superba subsp. superba. Controlling black rats at restoration sites appears integral to the successful restoration of this endangered plant species.     

Intra- and Interspecific Variation of the Mitochondrial Genome in RATTUS NORVEGICUS and RATTUS RATTUS: Restriction Enzyme Analysis of Variant Mitochondrial DNA Molecules and Their Evolutionary Relationships

Restriction endonuclease analysis has revealed extensive mtDNA polymorphism in two species of rats, Rattus rattus and Rattus norvegicus. Sequence divergence values for the eight detected R. norvegicus variants range from 0.2% to 1.8% and for the eight R. rattus variants, from 0.2% to 9.6%. Three of the most closely related R. norvegicus mtDNA's appear to differ by deletions/insertions of about 4 base pairs apiece. Restriction sites for seven enzymes have been mapped for 11 of these variants. The 31 intraspecific and 41 interspecific variant sites appear to be evenly distributed on the mtDNA molecule outside of the rRNA cistrons. The location of sites present in all the DNAs suggests that the rRNA genes and possibly the light strand origin of replication may be more highly evolutionarily conserved than other parts of the molecule. The sequence divergences among the mtDNAs of animals whose geographic origins are separated by major barriers, such as oceans, were significantly greater than those among animals found within large land masses, such as the continental United States. Dendrograms (phenograms), which have been constructed to depict the relationships among the various DNAs, indicate that East Asian members of the R. rattus species are more closely related to American rats of this species than to other Asian R. rattus animals from Sri Lanka. Moreover, it appears that R. norvegicus comprises a group taxonomically distinct from any of the R. rattus subspecies.     

岛屿生境下黄毛鼠种群的遗传变异

岛屿具有独特的生态系统,常被生态学家和进化生物学家视为研究生物进化的天然实验室,岛屿生物地理学也受到了越来越多科学家的关注。对舟山群岛8个面积不等岛屿的黄毛鼠(Rattus losea)种群进行了调查,分析了8个种群的遗传变异特征,对探讨岛屿理论中的种群动态和种群分化具有重要意义。采用线粒体分子标记技术,利用PCR扩增得到D-loop区基因序列815 bp,在330个黄毛鼠样本中共识别出15个单倍型,平均核苷酸多样性(P_i)为0.001,平均单倍型多样性(H_d)为0.364,表明舟山群岛黄毛鼠种群的遗传多样性较低。Tajima′s D中性检验显示除了小盘峙种群,均为显著负值(P0.01),表明种群受到了自然选择的作用,历史上发生过种群扩张。AMOVE显示,群体间的遗传分化指数平均值为0.745,处于较高的分化水平,表明遗传变异主要来自种群间,占74.5%。基于线粒体D-loop区序列构建的系统发育树和中值网络都表明8个岛屿的黄毛鼠种群起源于两个母系。此外,Mental检验显示不同岛屿种群间的遗传距离与岛屿间地理距离之间存在显著正相关关系(r=0.6077,P=0.004),种群遗传多样性与岛屿面积并未发现显著相关性(r=0.6255,P=0.1840)。研究结果可为岛屿黄毛鼠种群的微观演化以及一些岛屿物种的进化理论提供参考。     

Zoonotic and non-zoonotic helminths in black rats of rain-fed and irrigated areas of Swat,Khyber Pakhtunkhwa,Pakistan

Present study was conducted to get information on helminth parasites of zoonotic importance among the black rats of district Swat, Pakistan. Two hundred and sixty nine rats were captured from agricultural ecosystem of the district using live captured traps from 2011 to 2013. Captured rats were anesthetized and surveyed for the presence of ectoparasites, then were carefully dissected for investigation of endoparsites. Helminth parasites of 8 species were identified. Presence of parasite was noticed in 23.7% of sampled rats. The infection rates of sampled rats was given in order of their infectivity as Syphacia obvelata 13(4.83%), Aspiculuris tetraptera 13(4.83%), Heterakis spumosa 12 (4.46%), Hymenolepis spp. 9(3.34%), H.diminuta 8(2.97%), Hymenolepis fusa 4(1.48%), Lutziella microacetabularae 4(1.48%) and Lutziella spp. 1 (0.37%). No significant difference (P < 0.4289) was found in prevalence of parasites among areas, crops, crop stages and sex of the host while adult rats were found more infected than sub-adults. S. obvelata and A. tetraptera were the most common species of helminths while Lutziella sp., 1 (0.37%) was found only in one host. Rattus rattus (the black rat) was regarded as the host of helminth parasites of zoonotic importance, therefore the hidden health hazards of this rodent species needed to be considered to prevent infectivity of humans. Current study was concluded that Rattus rattus harbored a wide variety of helminth parasites which shows a hidden risk to inhabitants of the region. Monitoring rats’ population in settle areas and educating the local community about the risk of rat borne parasitic diseases transmission through rats appears to be absolutely essential.     

Ecology of cutaneous leishmaniasis in Sinai: linking parasites,vectors and hosts

Cutaneous leishmaniasis (CL) is a neglected clinical form of public health importance that is quite prevalent in the northern and eastern parts of Egypt. A comprehensive study over seven years (January 2005-December 2011) was conducted to track CL transmission with respect to both sandfly vectors and animal reservoirs. The study identified six sandfly species collected from different districts in North Sinai: Phlebotomus papatasi, Phlebotomus kazeruni, Phlebotomus sergenti, Phlebotomus alexandri, Sergentomyia antennata and Sergentomyia clydei. Leishmania (-)-like flagellates were identified in 15 P. papatasi individuals (0.5% of 3,008 dissected females). Rodent populations were sampled in the same districts where sandflies were collected and eight species were identified: Rattus norvegicus (n = 39), Rattus rattus frugivorous (n = 13), Rattus rattus alexandrinus (n = 4), Gerbillus pyramidum floweri (n = 38), Gerbillus andersoni (n = 28), Mus musculus (n = 5), Meriones sacramenti (n = 22) and Meriones crassus (n = 10). Thirty-two rodents were found to be positive for Leishmania infection (20.12% of 159 examined rodents). Only Leishmania major was isolated and identified in 100% of the parasite samples. The diversity of both the vector and rodent populations was examined using diversity indices and clustering approaches.     

洞庭湖区鼠类群落的物种多样性分析

通过对洞庭湖区黑线姬鼠褐家鼠主害区桃源的害鼠群落调查,揭示了平原农田生态类型区、丘陵农林复合生态类型区和山区林农复合生态类型区及其不同生境的鼠类群落的物种多样性。在人类干扰程度最高的平原生态类型区,鼠类群落的优势种突出,优势集中性指数最高,丘陵生态区次之,而具有大片森林、受干扰较低的山区林农复合生态区,优势集中性指数最低。物种多样性Shannon—Weiner指数和均匀性指数亦显示同样的规律：适度干扰的山区复合生态区的多样性指数最高,均匀性最好,丘陵生态区居中,平原生态区最低。不论何种生态类型区,农田生境鼠类群落的优势种都较突出,优势集中性指数也较高,群落多样性和均匀性较低;林地生境的优势集中性有较大下降,山区林地内的鼠种比丘陵区要多,优势集中性指数也较低,多样性指数和均匀度都有提高。林缘农田在同一生态类型不同生境内优势集中性最低、多样性指数和均匀性最高。比较不同生境鼠类群落的相似性,最不相似的群落是农田与受人类干扰较小的森林。这些现象说明人类的社会生产活动使害鼠群落的物种多样性降低、优势度下降、优势种突出、均匀性降低,形成了只利于少数几个种群栖息和生产发展的环境,最终导致少数种群的暴发,形成危害。但适度干扰能提高物种多样性。     

An olfactory basis for maternal discrimination of sex of offspring in rats (rattus norvegicus)

Lactating Long-Evans rats (Rattus norvegicus) were presented with three-day-old male and female pups that were either untreated, coated with collodion in the anogenital region or on the neck, or perfumed; or with female pups odorized with either male or female pup urine. As measured by related t-tests of maternal anogenital licking, male and female pups were discriminated in the untreated condition, but not when masking stimuli were present. Female pups treated with male urine elicited more licking than female pups treated with female urine. Overall, maternal licking was decreased by olfactory masking agents and increased by pup urine. It was concluded that olfactory stimuli from pups both stimulate maternal licking and serve as a basis for discriminating male and female offspring.     

Urban population genetics of slum‐dwelling rats (Rattus norvegicus) in Salvador,Brazil

Throughout the developing world, urban centres with sprawling slum settlements are rapidly expanding and invading previously forested ecosystems. Slum communities are characterized by untended refuse, open sewers and overgrown vegetation, which promote rodent infestation. Norway rats (Rattus norvegicus) are reservoirs for epidemic transmission of many zoonotic pathogens of public health importance. Understanding the population ecology of R. norvegicus is essential to formulate effective rodent control strategies, as this knowledge aids estimation of the temporal stability and spatial connectivity of populations. We screened for genetic variation, characterized the population genetic structure and evaluated the extent and patterns of gene flow in the urban landscape using 17 microsatellite loci in 146 rats from nine sites in the city of Salvador, Brazil. These sites were divided between three neighbourhoods within the city spaced an average of 2.7 km apart. Surprisingly, we detected very little relatedness among animals trapped at the same site and found high levels of genetic diversity, as well as structuring across small geographical distances. Most F_ST comparisons among sites were statistically significant, including sites <400 m apart. Bayesian analyses grouped the samples in three genetic clusters, each associated with distinct sampling sites from different neighbourhoods or valleys within neighbourhoods. These data indicate the existence of complex genetic structure in R. norvegicus in Salvador, linked to the heterogeneous urban landscape. Future rodent control measures need to take into account the spatial and temporal linkage of rat populations in Salvador, as revealed by genetic data, to develop informed eradication strategies.     

Antagonistic yeasts and thermotherapy as seed treatments to control Fusarium fujikuroi on rice

Bakanae disease, caused by Fusarium fujikuroi, is the most important seedborne disease of rice. Biological control and physical treatments can be effective tools to control seedborne diseases. Sixty-two isolates of yeasts and yeast-like fungi were obtained from different rice seeds. Four yeast isolates were selected in dual culture assays for mycelial growth inhibition, and in seed tests for reduction of infection rate. The isolates R23 and R26 were identified as Metschnikowia pulcherrima, the isolate R9 as Pichia guilliermondii, and the isolate SB1 as Sporidiobolus pararoseus. Rice seeds treated with P. guilliermondii R9, M. pulcherrima R23 and R26 significantly reduced the infection rate of F. fujikuroi, compared to some commercial biofungicides. The four selected yeasts reduced the bakanae disease severity in rice plants grown in greenhouse trials. Antagonist seed dressing resulted in reduction of the disease index from 93.0% in the untreated control to 20.0% in P. guilliermondii R9 treated seeds, and to 28.5% in M. pulcherrima R23 treated seeds. Selected antagonists were also used in combination with thermotherapy, which contributed to increase their efficacy. Thus, P. guilliermondii R9 and M. pulcherrima R23 combined with thermotherapy at 60 °C for 10 min decreased the bakanae disease index below 5%, and improved the seed germination rate compared to the single treatments, showing a seed priming effect. This is the first report about the use of antagonistic yeasts for seed dressing of rice to control F. fujikuroi on rice seeds, and biological treatment may be improved through combination with thermotherapy.     

Fecal Shedding of Zoonotic Food-Borne Pathogens by Wild Rodents in a Major Agricultural Region of the Central California Coast

Recent outbreaks of food-borne illness associated with the consumption of produce have increased concern over wildlife reservoirs of food-borne pathogens. Wild rodents are ubiquitous, and those living close to agricultural farms may pose a food safety risk should they shed zoonotic microorganisms in their feces near or on agricultural commodities. Fecal samples from wild rodents trapped on 13 agricultural farms (9 produce, 3 cow-calf operations, and 1 beef cattle feedlot) in Monterey and San Benito Counties, CA, were screened to determine the prevalence and risk factors for shedding of several food-borne pathogens. Deer mice (Peromyscus maniculatus) were the most abundant rodent species trapped (72.5%). Cryptosporidium species (26.0%) and Giardia species (24.2%) were the predominant isolates from rodent feces, followed by Salmonella enterica serovars (2.9%) and Escherichia coli O157:H7 (0.2%). Rodent trap success was significantly associated with detection of Salmonella in rodent feces, while farm type was associated with fecal shedding of Cryptosporidium and Giardia. Seasonal shedding patterns were evident, with rodents trapped during the spring and summer months being significantly less likely to be shedding Cryptosporidium oocysts than those trapped during autumn. Higher rodent species diversity tended to correlate with lower fecal microbial prevalence, and most spatiotemporal pathogen clusters involved deer mice. Rodents in the study area posed a minimal risk as environmental reservoirs of E. coli O157:H7, but they may play a role in environmental dissemination of Salmonella and protozoa. Rodent control efforts that potentially reduce biodiversity may increase pathogen shedding, possibly through promotion of intraspecific microbial transmission.     

Toxoplasmosis seroprevalence in urban rodents: a survey in Niamey,Niger

A serological survey of Toxoplasma gondii was conducted on 766 domestic and peridomestic rodents from 46 trapping sites throughout the city of Niamey, Niger. A low seroprevalence was found over the whole town with only 1.96% of the rodents found seropositive. However, differences between species were important, ranging from less than 2% in truly commensal Mastomys natalensis, Rattus rattus and Mus musculus, while garden-associated Arvicanthis niloticus displayed 9.1% of seropositive individuals. This is in line with previous studies on tropical rodents - that we reviewed here - which altogether show that Toxoplasma seroprevalence in rodent is highly variable, depending on many factors such as locality and/or species. Moreover, although we were not able to decipher statistically between habitat or species effect, such a contrast between Nile grass rats and the other rodent species points towards a potentially important role of environmental toxoplasmic infection. This would deserve to be further scrutinised since intra-city irrigated cultures are extending in Niamey, thus potentially increasing Toxoplasma circulation in this yet semi-arid region. As far as we are aware of, our study is one of the rare surveys of its kind performed in Sub-Saharan Africa and the first one ever conducted in the Sahel.     

Mast Pulses Shape Trophic Interactions between Fluctuating Rodent Populations in a Primeval Forest

How different functional responses of consumers exploiting pulsed resources affect community dynamics is an ongoing question in ecology. Tree masting is a common resource pulse in terrestrial ecosystems that can drive rodent population cycles. Using stable isotope (δ¹³C, δ¹⁵N) analyses, we investigated the dietary response of two fluctuating rodent species, the yellow-necked mouse Apodemus flavicollis and the bank vole Myodes glareolus, to mast events in Białowieża Forest (NE Poland). Rodent hair samples were obtained non-invasively from faeces of their predators for an 11-year period that encompassed two mast events. Spectacular seed crops of deciduous trees, namely oak Quercus robur and hornbeam Carpinus betulus, occur after several intermediate years of moderate seed production, with a post-mast year characterised by a nil crop. While a Bayesian isotopic (SIAR) mixing model showed a variety of potential vegetation inputs to rodent diets, the isotopic niche of the yellow-necked mouse was strongly associated with mast of deciduous trees (>80% of diet), showing no variation among years of different seed crop. However, bank voles showed a strong functional response; in mast years the vole shifted its diet from herbs in deciduous forest (∼66% of diet) to mast (∼74%). Only in mast years did the isotopic niche of both rodent species overlap. Previous research showed that bank voles, subordinate and more generalist than mice, showed higher fluctuations in numbers in response to masting. This study provides unique data on the functional response of key pulse consumers in forest food webs, and contributes to our understanding of rodent population fluctuations and the mechanisms governing pulse–consumer interactions.     

Response of lizard community structure to desert grassland restoration mediated by a keystone rodent

Many grasslands in the Chihuahuan Desert have transformed to shrublands dominated by creosotebush (Larrea tridentata). Grassland restoration efforts have been directed at controlling creosotebush by applying herbicide over large spatial scales. However, we have a limited understanding of how landscape-scale restoration affects biodiversity. We examined whether restoration treatments in southern New Mexico, USA have influenced the community structure of lizards, which are sensitive to shrub encroachment. We compared lizard community structure on 21 areas treated with herbicide from 7 to 29 years ago with paired untreated areas that were dominated by shrubs and matched by geomorphology, soils, and elevation. To examine mechanisms underlying responses to restoration, we tested whether the abundance of a grassland specialist, Aspidoscelis uniparens, depended on time since treatment, treatment area and isolation, and local habitat quality. Because lizards use rodent burrows as habitat, we tested whether community structure and A. uniparens abundance depended on the abundance of the keystone rodent, Dipodomys spectabilis. Treated areas had reduced shrub cover and increased grass cover compared to untreated areas. Lizard community composition differed strongly between areas, with four species responding to treatments. Divergence in community composition between treated–untreated pairs was greatest for old treatments (≥22 years), and community composition was influenced by D. spectabilis. In particular, the abundance of A. uniparens was greatest on old treatments with a high density of D. spectabilis. Overall, our results demonstrate lizard community structure responds to grassland restoration efforts, and keystone species can shape restoration outcomes. Reestablishment of keystone species may be a critical constraint on the recovery of animal biodiversity after habitat restoration.     

Sexual-size dimorphism in two synanthropic rat species: Comparison and eco-evolutionary perspectives

Sexual dimorphism is a common trait in many mammal species and sexual-size dimorphism (SSD) represents its commonest form. Rattus rattus and Rattus norvegicus are two cosmopolitan, polygynous species, for which a male-biased SSD has been anecdotally reported, but never quantified. In this work, we assessed the occurrence of SSD in both species and we tested the hypothesis that R. norvegicus has a more evident SSD than R. rattus, in agreement with their body mass-testes size ratio, intra-male aggressive behaviour and mating system. We collected weight data of 40 (20 males and 20 females) adult R. rattus and 27 (13 males and 14 females) adult R. norvegicus from 4 localities in Italy characterized by different habitat typologies. We used a t-test based on Bayesian inference to compare the SSD in both species. The results were in line with our expectation supporting a higher SSD in R. norvegicus than in R. rattus. This study aimed to identify the eco-evolutionary drivers of SSD, and provides further support to well established life history theories on two widely distributed rodent species.