Chubut Province Research Articles

Autecology of Wolfestheria smekali (Spinicaudata) from the Upper Jurassic (Cañadón Asfalto Formation), Patagonia, Argentina

Spinicaudatans are small branchiopod crustaceans also usually known as ‘Conchostraca’. They are easily recognizable by their short, laterally-compressed body inside of a characteristic bivalved, lightly-mineralized chitin carapace which is often the only preserved element of the group in the fossil record. The valves of the carapace are distinctive due to the presence of growth lines which are produced by the accumulation of successive cuticle layers retained after ecdysis. ‘Conchostracan’ paleoecology has been the subject of several previous studies—most focus on the paleoenvironment of the rock units in which the fossils were found. Few studies have been carried out on the paleoautecology of fossil taxa. In this work, an exploratory study was performed regarding the paleoautecology of the small clam shrimp Wolfestheria smekali Gallego and Monferran 2013, from the Cañadón Asfalto Formation (Upper Jurassic) in the Argentinean Chubut province in Patagonia, with the objective of understanding the ecological characteristics of individuals and populations within this species. Samples were collected from four stratigraphic levels in the Estancia La Sin Rumbo locality (in the Chubut River middle valley). W. smekali was found in association with the darwinuloid ostracod Penthesilenula sarytirmenensis Sharapova, mollusks assigned to the genus Diplodon Spix, and insects represented by larval cases from the order Trichoptera (caddisflies, Ostracindusia and Conchindusia). The population density of W. smekali in each sample was recorded and morphometric analyses were performed on a selected subsample of individuals. This technique allowed the discrimination of sexual dimorphism where males have a telliniform, ovate–elliptical shape, and females have a cycladiform, subcircular–subtriangular shape. Given the sex-ratio observed in the samples collected, it is likely that the species had a dioecious reproductive system (50% males, 50% females). It is hoped that the present work will give new insights into the dynamics of ancient ephemeral pools and serve as a foundation for future studies of fossil Spinicaudata.

New marsileaceous fossils from the Late Cretaceous of South America and a reevaluation of Marsileaceaephyllum

Herein we report new macrofossils and associated microfossils representing the aquatic fern family Marsileaceae from the Campanian to Maastrichtian Canadon del Irupe locality, La Colonia Formation, Chubut Province, Argentina. The macrofossils include compound leaves, detached leaflets, and sporocarps. The venation of the leaflets is consistent with the diagnosis of Marsileaceaephyllum, which we argue is poorly defined. Consequently, the circumscription and diagnosis of Marsileaceaephyllum are emended in order to limit the taxon to include only leaves or rhizomes bearing leaves with four leaflets that most resemble those of Marsilea among extant genera of Marsileaceae. The Canadon del Irupe leaves and leaflets are assigned to the new genus Mirasolita, erected to encompass compound leaves bearing two petiolulate leaflets, each leaflet having a reniform lamina and reticulate venation. The architecture of Mirasolita leaves and leaflets is distinct from that of leaves of any of the living marsileaceous genera. The stalked sporocarps are assigned to the new genus Lugiomarsiglia. They are attributed to Marsileaceae because each has a sclerenchymatous wall surrounding circular bodies interpreted as sporangia. Associated megaspores are assigned to Molaspora lobata, a geographically widespread, primarily Late Cretaceous dispersed spore taxon. The co-occurrence of Molaspora lobata with an extinct marsileaceous leaf form fits a pattern wherein Cretaceous Regnellidium-like megaspores are associated with or found in situ within marsileaceous macrofossils that display a variety of morphologies.

Una Nueva Especie deRetispiraKnight (Gastropoda, Bellerophontoidea) del Pérmico Inferior en la Provincia del Chubut, Argentina

A NEW SPECIES OF RETISPIRA KNIGHT (GASTROPODA, BELLEROPHONTOIDEA) FROM THE LOWER PERMIAN OF CHUBUT PROVINCE, ARGENTINA. A new species of Retispira Knight (Gastropoda, Bellerophontoidea) from the lower Permian of the Tepuel-Genoa Basin, Chubut Province, Argentina, is described. The specimens come from the Cisuralian Euphemites chubutensis - Palaeoneilo aff. concentrica Zone. Retispira patagoniensis sp. nov. is a small, subglobose, phaneronphalus bellerophontid characterized by having a broad selenizone with fine lunulae and spiral lirae. Spiral and colabral elements generate a reticulate pattern. The new species developed in both shallow marine and deltaic facies and its distribution was mainly affected by water turbidity, depth and temperature. Its feeding habit may have been herbivorous, probably as an algal foliage dweller.

Meiotic studies inBrachistosternus alienus(Scorpiones; Bothriuridae)

Abstract Brachistosternus Pocock 1893 is the most diverse genus of the scorpion family Bothriuridae. Only four species of the genus have been cytogenetically analyzed so far. We report herein the cytogenetic analysis of Brachistosternus alienus Lonnberg 1898 from Comallo (Rio Negro province, Argentina). This species is widely distributed in the Monte phytogeographic province, located in central and northern Argentine Patagonia. Meiotic cells of B. alienus from Comallo show 23 homomorphic achiasmatic bivalents. The karyotype of this species contains scarce AT-rich regions that may be associated with the heterochromatin of centromeric regions. Giacomozzi (1977) reports n = 14 for B. alienus from Chubut province. Unfortunately, it is not presently possible to determine if those specimens correspond to B. alienus or to a sympatric species, Brachistosternus angustimanus Ojanguren-Affilastro & Roig-Alsina 2001. These different chromosome numbers of the two populations analyzed may reflect the occurrence of a ...

Patellogastropoda and Vetigastropoda (Mollusca, Gastropoda) from the marine Jurassic of Patagonia, Argentina

Gastropod faunas from the Early Jurassic (Late Pliensbachian–Early Toarcian) marine deposits of Chubut Province, Argentina, are described from Lomas Occidentales, Cerro La Trampa and Puesto Currumil localities, representing eight species, three of them new. These are Scurriopsis? sp., Chartronella gradata sp. nov., Calliotropis? sp., Pleurotomaria sp., Leptomaria sp., Hamusina? wahnishae sp. nov., Colpomphalus musacchioi sp. nov. and Jurassiphorus? cf. triadicus Haas. The gastropod assemblage reported here testifies paleobiogeographical connections with other coeval gastropod associations from the western Tethys. However, Chartronella, Hamusina and Jurassiphorus may represent survivors of Triassic associations, considering the ancient seaway from Peru as the most plausible hypothesis for biotic exchange of these faunas during the Late Triassic–Early Jurassic boundary. An abundant and diverse invertebrate fauna such as corals, echinoderms, cephalopods, brachiopods, bivalves and other gastropods found in association with the gastropods described here characterises a shallow marine environment for the gastropod-bearing rocks.http://www.zoobank.org/urn:lsid:zoobank.org:pub:7B8EAFC0-3AC0-4F91-97A5-22AAC6A19909

First Record ofStreptocara formosensis(Nematoda: Acuariidae) from the Chubut Steamerduck,Tachyeres leucocephalus, Endemic to the Patagonian Coast, Southwest Atlantic

Streptocara formosensis (Nematoda: Acuariidae) is recorded for the first time from South America (Chubut Province, Argentina) and from the Chubut steamerduck, Tachyeres leucocephalus (Aves: Anatidae), enlarging its host and geographical distribution. To our knowledge, this is the first record of a parasite in this bird species.

A New Species ofBezziaKieffer from Argentinean Patagonia (Diptera: Ceratopogonidae)

Bezzia, galesa Spinelli, a new Patagonian species, is described in all stages and illustrated by using binocular, phase-contrast and scanning electron microscopy. Immatures were collected associated to submerged filamentous algae in an unnamed pond in western Chubut province, Argentina, and reared to adults in the laboratory. Adults and immatures of this new species are compared with the most similar species Bezzia ventanensis Spinelli, Bezzia, roldani Spinelli et Wirth and Bezzia blantoni Spinelli et Wirth. Details on the rearing process and feeding behavior in laboratory are given.

New record of anoplocephalid eggs (Cestoda: Anoplocephalidae) collected from rodent coprolites from archaeological and paleontological sites of Patagonia, Argentina

Results of paleoparasitological examination of rodent coprolites collected from archaeological and paleontological sites from Patagonia, Argentina, are present. Each coprolite was processed, rehydrated, homogenized, spontaneously sedimented and examined using light microscope. Coprolites and eggs were described, measured and photographed, and were compared with current faeces of Lagidium viscacia. Eggs with morphological features, attributed to an anoplocephalid cestode were found in samples collected from Cueva Huenul 1 (36°56′45″S, 69°47′32″W, Neuquén Province, Holocene) and Los Altares Profile (43º53′35″S, 68º23′21″W, Chubut Province, Late Holocene). These are the first findings of this anoplocephalid from faecal material from patagonic rodents.

First Record of Conifer Wood from the Cañadón Asfalto Formation (Early-Middle Jurassic), Chubut Province, Argentina

Abstract. A new fossil conifer wood —Brachyoxylon currumilii sp. nov.— is described from the Lower—Middle Jurassic of Chubut Province (Argentina). The specimens were collected at a locality where the Canadon Asfalto Formation is exposed, in the vicinity of the Cerro Condor village. The studied wood is characterized by mixed pitting in radial tracheid walls (predominantly uniseriate), araucarioid cross fields, low uniseriate rays and the absence of resin canals. The use of transmitted light and epifluorescence microscopy together with SEM imaging allowed the identification of additional characters such as the presence of pitting with torus-margo and compression wood. These characters are discussed in terms of their systematic relevance. On these grounds, the systematic affinity of the studied wood is discussed and linked to the extinct conifer family Cheirolepidiaceae, one of the dominant plant groups during the Jurassic and Cretaceous in Patagonia.

Current status of the threatened Olrog’s GullLarus atlanticus: global population, breeding distribution and threats

SummaryOlrog’s GullLarus atlanticusbreeds only in Argentina and is currently categorized as “Vulnerable”. Knowledge of the location of colonies and an updated understanding of human activities that may impact their breeding populations are crucial to the development of adequate conservation and management actions. In this paper we update the breeding distribution and abundance of Olrog’s Gull, using information from three aerial surveys (2004, 2007 and 2009) in its main breeding area, Buenos Aires Province, complemented by additional nest counts in southern Chubut Province, covering its entire breeding range. We also provide an updated and more detailed account of threats faced by Olrog’s Gulls at their nesting grounds, and summarise progress made towards their protection. The number of breeding sites was 7–12 per year, with locations differing among years. Five previously unrecorded breeding locations were identified. Colony size ranged from 5 to 3,540 breeding pairs, with the total breeding population 4,860–7,790 pairs, 98% of which nest in southern Buenos Aires Province. The main threats faced by breeding Olrog’s Gulls include coastal development, pollution, sport fishing and unregulated tourism and recreational activities. Recent strengthening of the protected area system in Argentina has resulted in all known breeding sites, with the exception of Isla Brightman, falling within protected areas. We need comprehensive, simultaneous surveys to track global population trends. Despite enhanced protection of Olrog’s Gull breeding populations, efforts are still needed to ensure that guidelines for their protection are included in management plans and that these are implemented effectively.

Regnellidium (Salviniales, Marsileaceae) Macrofossils and Associated Spores from the Late Cretaceous of South America

Premise of research. Fossils representing aquatic ferns with clear affinities to extant Regnellidium (Salviniales, Marsileaceae) are reported for the first time from Upper Cretaceous sediments of the La Colonia Formation, Chubut Province, Argentina.Methodology. Preserved organs including rhizomes bearing roots, compound leaves, and associated putative sporocarps were collected from the Cerro Bosta and Quebrada del Helecho localities of the La Colonia Formation. Spores were macerated for the macrofossil-bearing sediments of the Cerro Bosta locality and examined with SEM.Pivotal results. The macrofossils are morphologically similar to extant Regnellidium diphyllum. The fossil plants are rhizomatous, with the rhizomes bearing roots and leaves with two leaflets. The leaflets have dichotomizing venation and a marginal vein. Associated megaspores attributed to Molaspora lobata and microspores of the Crybeloporites type are also comparable to those of extant Regnellidium.Conclusions. These fossils represent the ...

Pararaucaria delfueyoi sp. nov. from the Late Jurassic Cañadón Calcáreo Formation, Chubut, Argentina: Insights into the Evolution of the Cheirolepidiaceae

The discovery of 16 cylindrical conifer seed cones at the Estancia Vilán locality in the Late Jurassic Cañadón Calcáreo Formation of Chubut Province, Patagonia, Argentina, provides anatomically preserved specimens, allowing for the description of a second species of Pararaucaria (Cheirolepidiaceae). The new species, Pararaucaria delfueyoi, is similar in general features to the type species, Pararaucaria patagonica, but has a specifically diagnostic combination of characters that include cone size, seed number, features of histology, and seed size. Specimens are cylindrical with a narrow axis that bears helically arranged bract/scale complexes. The bract and scale diverge from the axis at ∼90° and separate from each other almost immediately. The ovuliferous scale extends toward the margin of the cone and then arches over to enclose two inverted nonwinged seeds within a pocket of tissue. Although the specimens are abraded such that the distal regions of the ovuliferous scales are not preserved, this combination of morphological and histological characters allows for the assignment of P. delfueyoi to the Cheirolepidiaceae with confidence. The co-occurrence of this cone with an undescribed species of Araucaria extends the geographic and stratigraphic ranges of this association, which previously has been known only from the Middle Jurassic of Santa Cruz Province of Patagonia. This extends the knowledge of anatomical variation among seed cones of Cheirolepidiaceae and improves our understanding of homology relationships for conifer seed cone structures.

High-precision U–Pb geochronology and a new chronostratigraphy for the Cañadón Asfalto Basin, Chubut, central Patagonia: Implications for terrestrial faunal and floral evolution in Jurassic

The fluvial, lacustrine and tuffaceous sedimentary succession of the Cañadón Asfalto continental basin exposed in the Argentinean Chubut Province of central Patagonia preserves an extraordinary record of Jurassic fauna and flora that marks key events in the evolution of Dinosauria, early mammals and major South American plant groups. However, basin-wide correlation of the fossiliferous units is complicated by fault displacements, unconformities and repetitive lithofacies. New U–Pb analyses of zircon (CA-TIMS method) from five primary tuff beds interstratified with the lacustrine strata establish a new chronostratigraphic framework for the sedimentary and volcanic units of Cañadón Asfalto Basin, constraining ca. 33m.y. of depositional history and biotic evolution that spans nearly all three epochs of the Jurassic. Five major vertebrate- and plant-rich stratigraphic intervals have been identified, and are being actively investigated, that range in age from Pliensbachian to Kimmeridgian (or younger). Our combined biostratigraphic and high-precision geochronologic results indicate that the major faunal turnover of the sauropodomorph dinosaurs which led to the rise of the eusauropods took place in the Early Jurassic, earlier than previously recognized. Similarly, the first successful radiation of the ornithischian dinosaurs (heterodontosaurids), as well as the evolutionary diversifications of the araucarian conifers and the osmundaceous ferns, all occurred before the end of the Early Jurassic. The diverse palynofloral assemblage of the Cañadón Calcáreo Formation that was once considered to be early Cretaceous in age, is now entirely constrained to the Late Jurassic.

A new acaremyid rodent (Hystricognathi: Octodontoidea) from the middle Miocene of Patagonia (South America) and considerations on the early evolution of Octodontoidea.

Octodontoidea is the most speciose and ecologically diverse superfamily of caviomorph rodents. The systematic relationships of modern octodontoids is moderately accepted, however, the relationships of fossils (from the Eocene?-middle Miocene) are not clear. In recent years the hypothesis of a complex early evolution of the superfamily has emerged, with "basal octodontoids" representing different evolutionary lineages. The extinct family Acaremyidae may represent one such lineage, consisting of the genera Acaremys, Sciamys, Galileomys, and variably Platypittamys. In this work we describe a new octodontoid rodent recorded in post-Colloncuran? levels exposed at the locality of El Petiso, Northwest of Chubut Province, Argentina. Based on a systematic analysis of dental characters, we conclude that the new specimens correspond to a new species of Sciamys. Additionally, if the post-Colloncuran age for El Petiso is verified, the new species will extend the temporal range of the family Acaremyidae until, at least, the late middle Miocene, as well as the temporal range for the genus Sciamys from the Santacrucian SALMA. Our phylogenetic analyses corroborate the position of the new species as a member of Sciamys, and confirm that Acaremyidae represents an extinct family from Patagonian South America that lived until the middle Miocene. Massoiamys obliquus qualifies as morphological ancestor that pre-announces the octodontiform tooth pattern of octodontids. Thus, the octodontiform tooth pattern appears at least twice within the superfamily Octodontoidea.

Three new species and one new record of Campylaimus (Diplopeltidae, Nematoda) from Argentine coasts (Buenos Aires and Santa Cruz, Argentina)

Two new Campylaimus species from Arroyo Pareja, Buenos Aires province and one new species and one new record of Campylaimus from Puerto San Julián, Chubut province are described. The three species are characterized by the shape of the copulatory apparatus of the male and the presence of precloacal papillae. Campylaimus bonariensis sp. nov. has slender and arcuate spicules, with well-developed cephalization at the proximal end, tubular gubernaculum and three precloacal papillae; Campylaimus arcuatus sp. nov. has curved spicules, with well-developed cephalization at the proximal end, gubernaculum with dorso-caudally directed apophysis and five precloacal papillae; Campylaimus patagonicus sp. nov. has slender and arcuate spicules without proximal cephalization, gubernaculum with dorso-caudally directed apophysis and two precloacal papillae. An emended diagnosis of the genus Campylaimus and an identification key to species based on male characters are given.

Association of phosphate with rhyolite glass in marine Neogene tuffs from Patagonia, Argentina

AbstractThe precipitation/replacement of Ca‐phosphate is a complex process that commonly takes place during the early diagenesis in marine sediments. The unusual occurrence of shallow marine, early diagenetic phosphatic deposits associated with glassy tuffs in the Neogene Gaiman Formation, in the Chubut Province, Patagonia, Argentina, constitutes a good case example for the study of replacement and precipitation of Ca‐phosphate on an unstable substrate. Isocon diagrams illustrate that chemical changes during glass diagenesis include gains in loss on ignition and Ca, and losses of K. These changes are the result of glass hydration during sea water–glass interaction, together with adsorption and diffusion of ions into the bulk shard; combined, these represent an incipient process of volcanic glass replacement by Ca‐phosphate. Subsequent early diagenetic P enrichment in the pore solutions led to phosphate precipitation, associated with pitting on the glass shards and pumice. The associated development of a reactive surface promoted the incorporation of P and Ca into their margins. Lastly, precipitation of calcium phosphate filled the vesicles and other open cavities, inhibiting further glass dissolution. The high porosity and reactivity of the volcanic glass provided an appropriate substrate for phosphate precipitation, leading to the development of authigenic apatite concretions in the volcanic‐glass bearing strata of the Gaiman Formation. This research is of significance for those concerned with marine phosphatic deposits and sheds light on the processes of early diagenetic phosphate precipitation by replacement of an atypical, unstable substrate like hydrated volcanic glass.

Huevos De Saurópodos Del Aptiano-Albiano, Formación Cerro Barcino (Patagonia, Argentina): Un Enigma Paleoambiental y Paleobiológico

SAUROPOD EGGS FROM THE APTIAN-ALBIAN CERRO BARCINO FORMATION, CHUBUT (PATAGONIA, ARGENTINA): A PALEOENVIRONMENTAL AND PALEOBIOLOGICAL ENIGMA. Here are described the first eggs and eggshell fragments from the Lower Cretaceous Chubut province. The two eggs and eggshell materials come from the Huaniman locality at the north-central region of Chubut. In this paper, we provide a paleontological description of the materials to infer their paleoenvironmental setting and we offer a morphological comparison with other South American dinosaur eggs. The egg materials were found in fine tuffaceous sandstone from a proximal floodplain deposits associated to sinuous and multi-episodic river channels, belonging to the Cerro Castaño Member (Aptian-Albian; Cerro Barcino Formation). The eggshell morphology is similar to that of megaloolithid eggs (a paraphyletic group in egg parataxonomy) known from Patagonia such as Auca Mahuevo, Neuquen, positively identified as sauropod titanosaurs on the basis of in ovo embryos, and Salitral Moreno, Rio Negro. However, the new specimens from Chubut exhibit structural features of the eggshell not previously reported such as a horizontal network of pore canals clearly visible near and beneath the outer nodular eggshell surface, similar in morphology but differently placed than in the Auca Mahuevo eggs —where it overlays the membrana testacea. This morphological feature and the 1.5 mm thick eggshell may illustrate a novel adaptation to this specific nesting environment. Although only two isolated eggs were found in Huaniman, this discovery suggests the potential for the existence of a more substantial nesting site in the area.

Palaeoenvironmental and palaeoecological implications from body fossils and ovipositions of Odonata from the Eocene of Patagonia, Argentina

Odonata are beginning to be well recorded in the Eocene of Patagonia, Argentina. They are represented by body fossils and traces in three localities. Oviposition scars are recorded in Río Pichileufú (Lutetian: 47.7 Ma; Río Negro province) and Laguna del Hunco (Ypresian: 52.2 Ma; Chubut province), nymphs in Confluencia (Ypresian?; Río Negro), and adults (wings) in Laguna del Hunco. The absence of different stages in given localities could depend on different factors, such as as environmental, taphonomical and/or sampling bias. Laguna del Hunco is well sampled and the absence of nymphs seems to depend on taphonomical factors since there are other preimaginal aquatic inhabitants of the lake, such as Trichoptera nymph cases. Confluencia has not been well sampled and adults could be absent due to a sampling bias. The nymphs of Confluencia indicate a water body with low energy flux. Ovipositions in Laguna del Hunco and Río Pichileufú are made on terrestrial leaves of bushes and trees and have three different morphologies. Leaves are interpreted to be alive when oviposition was done as they show tissue reactions associated to the injuries. Wrinkled wings at Laguna del Hunco are interpreted to be signals of predation probably by birds or mammals.

Epiphytism in a subtidal natural bed of Gracilaria gracilis of southwestern Atlantic coast (Chubut, Argentina)

The diversity of epiphytes, their temporal abundance variation and the anatomical structure of host–epiphyte interfaces were studied in the agarophyte Gracilaria gracilis from a natural bed in Bahia Bustamante, Chubut Province, Argentina. Twenty-nine algal species were recorded as epiphytes during 2 years of monthly sampling (March 2006–February 2008). Total epiphyte density ranged between 0.037 ind. cm−2 (November 2006) and 39.37 ind. cm−2 (April 2007), with higher density values throughout the second sampling year. Ceramiales species were the most abundant epiphytes. The density of Ceramium rubrum ranged from 0.09 ind. cm−2 (52 % of the total amount) in September 2006 to 17.4 ind. cm−2 (44.18 % of the total amount) in April 2007. Epiphyte infection was more dependent on spore recruitment and sporeling development, especially on thalli derived from fragmentation, than on seasonal environmental variations. The different infections were analysed, taking into account the epiphytic attachment strength and invasiveness and the degree of damage inflicted on the host. Calothrix confervicola was one of the most abundant species. This epiphyte, weakly attached to the host surface, generated no host tissue damage. In contrast, C. rubrum, Polysiphonia abscissa and other Ceramiales were the species that caused more damage to the host because their rhizoids penetrated the cortical portion of the host thallus, sometimes reaching the medullary tissue. Some generalisations and characterisations of the different epiphyte groups in relation to their consequences to Gracilaria spp. are presented.

Summer—autumn distribution and abundance of the hantavirus host,Oligoryzomys longicaudatus, in northwestern Chubut, Argentina

We examined population density of Oligoryzomys longicaudatus (colilargo) and prevalence of Andes virus (ANDV) antibody at regional and landscape spatial scales in northwestern Chubut Province (Argentina) and contrasted it with climatic variables recorded by meteorologic stations near the study area. Mice were trapped in late summer–early fall (March–April) for 3 years (2007–2009). The composition of the rodent assemblage and species representation in the community varied among years, regions (forest, ecotone, and steppe), and landscape units (Nothofagus and Austrocedrus forests, sweet briar shrublands, and without sweet briar shrublands). Colilargos occurred in all regions and landscape units within the study area, from dense forest to open habitats such as steppe. The species dominated the rodent assemblages of ecotone and forest at a regional scale and the assemblages in sweet briar shrublands and Austrocedrus forests at a landscape scale. Abundance of colilargos also varied among periods, regions, and landscape units. Antibodies to ANDV were found in all regions but not in every landscape unit. Thus there is a potential for human hantavirus pulmonary syndrome (HPS) cases to occur not only in forests and shrublands, but also in steppe. At a landscape scale, Nothofagus forests appeared to pose a higher risk than Austrocedrus in wet years, because colilargo abundance and ANDV antibody prevalence were significantly greater. Within ecotone, sweet briar shrublands posed greater risk than habitats without sweet briar. Sweet briar shrublands were the landscape unit with the highest colilargo abundances during the driest periods. Sweet briar shrublands may play an important role in HPS dynamics, and should be considered when designing prevention policies.