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Seaports are introduction hotspots for invasive alien species (IAS). This is especially true for rodents, which have accompanied humans around the globe since the earliest days of ocean-going voyages. The rapid spread of IAS soon after arrival in a new environment is facilitated by further human-mediated transport or landscape features, like roads. By measuring genetic diversity and structure to investigate dispersal pathways, we gained insight into the transport, spread and establishment stages of a biological invasion, leveraging the most common rodent species (R. norvegicus) in this setting. We characterized the genetic structure of three Norway rat populations along a busy industrial road used by trucks to access the Port area in Paranaguá city (Brazil). A total of 71 rats were genotyped using 11 microsatellite markers. The results revealed a pattern of gene flow contrary to the expected stepping-stone model along the linear transect, with the two furthest apart populations being clustered together. We hypothesize that the observed outcome is explained by natural dispersal along the corridor being lower than human-mediated transport. The sampled area furthest from the port is a gas station frequented by trucks which are considered the most likely mode of transportation. In terms of management strategies, we suggest more emphasis should be put on cargo surveillance to lower the risk of Norway rat dispersal, not only for biosecurity, but also for sanitary reasons, as this port is a major grain trading point.

The Atlantic forest possess 1,361 vertebrate species of which 567 are endemic. Rodentia and Didelphimorphia comprise 71% of the endemic mammals observed in this biome. In Brazil, these animals still lack basic information about their biology, distribution, and even total wealth. This study aimed to identify the species of marsupials and rodents present in Rio da Onça State Park and to characterize the morphology of guard hairs and chromosomal set thereof, besides verify the composition of small non-flying mammals in different environments and vegetation strata. Thirteen field campaigns were conducted and as an additional effort, three lines of pitfall traps were installed. The total sampling effort was 6.633 traps and 1.181 buckets spread over 69 nights of sampling, which resulted in 196 captures of 166 individuals of 12 species. Seven species of Rodentia Order were recorded: Akodon montensis, Delomys sublineatus, Euryoryzomys russatus, Juliomys pictipes, Nectomys squamipes,Oligoryzomys nigripes and Thaptomys nigrita and five species of marsupials (Didelphimorphia Order): Didelphis aurita, Gracilinanus microtarsus, Metachirus nudicaudatus, Marmosa paraguayana and Monodelphis iheringi. Trichological and cytogenetic results were consistent with those available in the literature. Regarding the vertical stratification, only seven captures were made in trees. Four of the species Marmosa paraguayana, two Didelphis aurita, and one Akodon montensis. Therefore, in the environment of the lowlands of the study area, sampling carried out on tree and shrub extract of the understory did not contribute to the increase of the species list.

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Bibimys is a genus still poorly known in its basic aspects, such as systematics, natural history and geographic distribution. In Brazil, only Bibimys labiosus is recorded, with occasional records spread in time and space. This paper presents four new localities of the species in Araucaria Forest, Paraná state, extending its distribution 150 km southwards. Additionally, a map of the known distribution of the species in Brazil and in Araucaria Forest is provided. The records point toward the lack of knowledge about basic aspects of the small non-flying mammal fauna in the plateau regions of Brazil.

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Genetic diversity can affect population viability and can be reduced by both acute and chronic mechanisms. Using the history of the establishment and management of two invasive rat species on Tetiaroa atoll, French Polynesia, we investigated the intensity and longevity of contrasting population bottleneck mechanisms on genetic diversity and bottleneck signal. Using microsatellite loci we show how both a chronic reduction over approximately 50 years of a Rattus exulans population caused by the arrival of its competitor R. rattus, and an acute reduction in a R. rattus population caused by a failed eradication approximately 10 years ago, caused similar magnitudes of genetic diversity loss. Furthermore, these strong bottleneck signals were in addition to the lasting signal from initial colonisation by each species many decades to centuries earlier, characterising a genetic paradox of biological invasion. These findings have implications for the study of population genetics of invasive species, and underscore how important historical context of population dynamics is when interpreting snapshots of genetic diversity.