PHYLOGENETIC ANALYSIS OF SOME BASAL EARLY CAMBRIAN TRILOBITES, THE BIOGEOGRAPHIC ORIGINS OF THE EUTRILOBITA, AND THE TIMING OF THE CAMBRIAN RADIATION

This paper presents a phylogenetic analysis of the “Fallotaspidoidea,” a determination of the biogeographic origins of the eutrilobites, and an evaluation of the timing of the Cambrian radiation based on biogeographic evidence. Phylogenetic analysis incorporated 29 exoskeletal characters and 16 ingroup taxa. In the single most parsimonious tree the genusFallotaspidellaRepina, 1961, is the sister taxon of the sutured members of the Redlichiina Richter, 1932. Phylogenetic analysis is also used to determine the evolutionary relationships of two new species of “fallotaspidoids” distributed in the White-Inyo Range of California that have been previously illustrated but not described. These species had been referred toFallotaspisHupé, 1953, and used to define the occurrence of the eponymousFallotaspisZone in southwestern Laurentia. However, these two new species need to be reassigned toArchaeaspisRepinainKhomentovskii and Repina, 1965. They are described asArchaeaspis nelsoniandA. macropleuron.Their phylogenetic status suggests that theFallotaspisZone in southwestern Laurentia is not exactly analogous to theFallotaspisZone in Morocco, where that division was originally defined. Thus, changes to the biostratigraphy of the Early Cambrian of southwestern Laurentia may be in order. Furthermore, specimens of a new species referable toNevadiaWalcott, 1910, are recognized in strata traditionally treated as within theFallotaspisZone, which is held to underlie theNevadellaZone, suggesting further biostratigraphic complexity within the basal Lower Cambrian of southwestern Laurentia.Phylogenetic analyses of the Olenellina and Olenelloidea, along with the phylogenetic analysis presented here, are used to consider the biogeographic origins of the eutrilobites. The group appears to have originated in Siberia. Biogeographic patterns in trilobites, especially those relating to the split between the Olenellid and Redlichiid faunal provinces are important for determining the timing of the Cambrian radiation. Some authors have argued that there was a hidden radiation that significantly predated the Cambrian, whereas others have suggested that the radiation occurred right at the start of the Cambrian. The results from trilobite biogeography presented here support an early radiation. They are most compatible with the notion that there was a vicariance event relating to the origin of the redlichiinid trilobites, and thus the eponymous Redlichiid faunal province, from the “fallotaspidoids,” whose representatives were part of the Olenellid faunal province. This vicariance event, based on biogeographic patterns, is likely related to the breakup of Pannotia which occurred sometime between 600–550 Ma, suggesting that the initial episodes of trilobite cladogenesis occurred within that interval. As trilobites are relatively derived arthropods, this suggests that Númerous important episodes of metazoan cladogenesis precede both the earliest trilobitic part of the Early Cambrian, and indeed, even the Early Cambrian.

Critical comments on the South Atlantic puzzle of reef fish biogeography [J.‐C. Joyeux, S.R. Floeter, C.E.L. Ferreira &amp; J.L. Gasparini (2001) Biogeography of tropical reef fishes: the South Atlantic puzzle. <i>Journal of Biogeography</i>, 28, 831–841

Collections‐based systematics and biogeography in the 21st century: A tribute to Dr. Vicki Funk

The Cambrian radiation is that key episode in the history of life when a large number of animal phyla appeared in the fossil record over a geologically short period of time. Over the last 20 years, scientific understanding of this radiation has increased significantly. Still, fundamental questions remain about the timing of the radiation and also the tempo of evolution. Trilobites are an excellent group to address these questions because of their rich abundance and diversity. Moreover, their complex morphology makes them readily amenable to phylogenetic analysis, and deducing the nature of macroevolutionary processes during the Cambrian radiation requires an understanding of evolutionary patterns. Phylogenetic biogeographic analysis of Early Cambrian olenellid trilobites, based on a modified version of Brooks Parsimony Analysis, revealed the signature of the breakup of Pannotia, a tectonic event that most evidence suggests is constrained to the interval 600 to 550 Ma. As trilobites are derived metazoans, this suggests the phylogenetic proliferation associated with the Cambrian radiation was underway tens of millions of years before the Early Cambrian, although not hundreds of millions of years as some have argued.Phylogenetic information from Early Cambrian olenellid trilobites was also used in a stochastic approach based on two continuous time models to test the hypothesis that rates of speciation were unusually high during the Cambrian radiation. No statistical evidence was found to support this hypothesis. Instead, rates of evolution during the Cambrian radiation, at least those pertaining to speciation, were comparable to those that have occurred during other times of adaptive or taxic radiation throughout the history of life.

Biogeographic patterns from early Cambrian trilobites are used to evaluate the nature and timing of the Cambrian radiation. Results from a phylogenetic biogeographic analysis reveal that patterns of vicariance are compatible with a vicariant distribution of trilobites across what were originally joined elements of the supercontinent Pannotia; further, there is limited evidence for coordinated range expansion or geo-dispersal by these trilobites. As Pannotia had split apart sometime between 550-600 Ma this suggests that trilobites, and by extension several other metazoan taxa, had begun to diversify by this interval. This result suggests that there may have been some period of cryptic diversification by metazoans prior to the Cambrian radiation, though the inferred length of this interval is not as long as that invoked by some molecular studies. Perhaps trilobites existed at low population densities in marginal environments before they became paleontologically emergent. Even though the results suggest some apparent gap in the fossil record, the evolutionary signature of this gap is still preserved in the paleobiological patterns from the fossil record, indicating that the fossil record is still the one best source of data on the nature of key episodes in the history of life, like the Cambrian radiation.

Is biogeography emerging from its identity crisis?

AimUnderstanding the formation and maintenance of biogeographical breaks is fundamental for developing analyses related to biodiversity and conservation. Biogeographical patterns along China's coast are changing dramatically in the face of climate change and alterations in land‐use. In this paper, we sought to clarify the mechanisms responsible for the formation and maintenance of a biogeographical barrier on China's coast.LocationCoastline of northern China.MethodsWe have reviewed literature of research related to biogeographical and phylogeographical patterns of intertidal macrobenthos along the coast of Jiangsu Province and adjacent areas, summarized the distribution patterns and biogeographical breakers. We have also reviewed literature about the processes and drivers on coastal biogeographical breaks, to clarify the mechanisms acting to the northward shift of the biogeographical break.ResultsThe Yangtze (Changjiang) River Estuary Biogeographical Barrier (YREBB) at 30°–31°N, which serves as a coastal biogeographical boundary for the Cold Temperate Northwest Pacific Province and the Warm Temperate Northwest Pacific Province for marine species, has moved northward to ~33°–34°N due to the changes in habitat continuity, oceanographic circulation and climate factors. Consequently, a new biogeographic barrier for intertidal macrobenthos, the Subei Biogeographical Barrier (SBB) on the central coast of Jiangsu Province, has emerged.Main conclusionsThe formation and maintenance of the SBB are closely related to the larval dispersal potential, larval settlement success and post‐settlement population establishment, all of which have been profoundly influenced by anthropogenic environmental changes. The northward shift of the YREBB and the appearance of the SBB provide an excellent model system for investigating the impacts of climate change and land‐use change on coastal biogeographic patterning and for clarifying the mechanisms underlying the formation and maintenance of biogeographical barriers in the face of the unprecedented environmental changes.

Geological data and basin subsidence modeling results from the western margin of North America (Laurentia) have supported a late Ediacaran to early Cambrian age for the onset of passive margin sedimentation following the protracted breakup of Rodinia. However, several recent studies posit that increased early Cambrian subsidence may instead be driven primarily by eustatic sea-level rise. Here, we present new quantitative subsidence analyses of Neoproterozoic−Paleozoic strata in the southern Great Basin, USA, using decompaction, backstripping, and Bayesian thermal subsidence modeling methods that statistically propagate uncertainties. Our results support polyphase extension along the ancestral western margin of Laurentia and are consistent with a rift-drift transition in southwestern Laurentia that broadly overlaps with the Ediacaran−Cambrian transition. Although we do not discount the role of eustasy in facilitating increased accommodation space in the early Cambrian, the magnitude and local variability of this signal require additional tectonic forcings.

BackgroundPhryma leptostachya L. is a notable example of a species with a disjunct distribution, found in both East Asia and Eastern North America. Despite the striking morphological similarities between these geographically isolated populations, molecular evidence suggests that they may have diverged sufficiently to be considered distinct taxa.ResultsTo clarify this, we analyzed the plastomes of P. leptostachya from Korea, Russia, and the USA. Their sizes ranged from 152,974 to 153,325 bp, each containing 113 genes. Differences were observed in the boundaries between large single copy (LSC)/IRa and IRb/LSC. In P. leptostachya_USA, the rps19 gene extended 30–31 bp into the IRa, and the rpl2 gene contracted 51–53 bp at the IRa/b compared to those of P. leptostachya_Korea and P. leptostachya_Russia, suggesting that expansion of the inverted repeat (IR) region occurred in P. leptostachya_USA. Regions such as psbZ-trnG, ccsA-ndhD, petA-psbJ, and psbC-trnS were identified as hotspots with sequence differences in the plastome, indicating differences among P. leptostachya variants. Phylogenetic analysis showed that P. leptostachya from Korea and Russia formed monophyletic groups, while the variety from the USA was paraphyletic. The divergence of P. leptostachya_USA occurred during the Pliocene, about 5.25 million years ago (MYA), whereas the split between P. leptostachya_Korea and P. leptostachya_Russia is estimated to have occurred approximately 0.87 MYA during the Pleistocene. The results also reveal that the family Phrymaceae underwent multiple dispersal and vicariance events from North America to East Asia, offering key insights into the phylogenetic relationships between P. leptostachya populations from Korea, Russia, and the USA. Based on the evidence, it is likely that P. leptostachya originated in North America and later migrated to East Asia via the Russian Far East and the Bering Land Bridge.ConclusionsIn conclusion, our study demonstrates clear molecular differences among P. leptostachya populations from various geographic locations, suggesting that these populations should be recognized as distinct species rather than conspecifics.

Interactive forces between competition and habitat filtering drive many biogeographic patterns over evolutionary time scales. However, the responsiveness of assemblages to these two forces is highly influenced by spatial scale, forming complex patterns of niche separation. We explored these spatial dependencies by quantifying the influence of phylogeny and functional traits in shaping present day native terrestrial mammal assemblages at multiple scales, principally by identifying the spatial scales at which niche evolution operates. We modelled the distribution of 53 native terrestrial mammal species across New South Wales, Australia. Using predicted distributions, we estimated the range overlap between each pair of species at increasing grain sizes (~0.8, 5.1, 20, 81, 506, 2,025, 8,100 km2). We employed a decision tree to identify how interactions among functional traits and phylogenetic relatedness translated to levels of sympatry at increasing spatial scales. We found that Australian terrestrial mammals displayed phylogenetic over-dispersion that was inversely related to spatial scale, suggesting that ecological processes were more influential than biogeographic sympatry patterns in defining assemblages of species. While the contribution of phylogenetic relatedness to patterns of co-occurrence decreased as spatial scale increased, the reverse was true for habitat preferences. At the same time, functional traits also operated at different scales, as dietary preferences dominated at local spatial scales (<10 km2) while body mass has a stronger effect at larger spatial scales. Our findings show that ecological and evolutionary processes operate at different scales and that Australian terrestrial mammals diverged slower along their micro-scale niche compared to their macro-scale niche. By combining phylogenetic and niche methods through the modelling of species distributions, we assessed whether specific traits were related to a particular niche. More importantly, conducting multi-scale spatial analysis avoids categorical assignment of traits-to-niches, providing a clearer relationship between traits and a species ecological niche and a more precise scaling for the axes of niche evolution.

The phylogenetic relationships within the piranhas were assessed using mitochondrial sequences with the aim of testing several hypotheses proposed to explain the origin of Neotropical diversity (palaeogeography, hydrogeology and museum hypotheses). Sequences of the ribosomal 16S gene (510 bp) and control region (980 bp) were obtained from 15 localities throughout the main South American rivers for 21 of the 28 extant piranha species. The results indicate that the genus Serrasalmus is monophyletic and comprises three major clades. The phylogeographical analyses of these clades allowed the identification of five vicariant events, extensive dispersal and four lineage duplications suggesting the occurrence of sympatric speciation. Biogeographical patterns are consistent with the prediction made by the museum hypothesis that lineages from the Precambrian shields are older than those from the lowlands of the Amazon. The vicariant events inferred here match the distribution of the palaeoarches and several postdispersal speciation events are identified, thereby matching the predictions of the palaeogeography and hydrogeology hypotheses, respectively. Molecular clock calibration of the control region sequences indicates that the main lineages differentiated from their most recent common ancestor at 9 million years ago in the proto Amazon-Orinoco and the present rate of diversification is the highest reported to date for large carnivorous Characiformes. The present results emphasize that an interaction among geology, sea-level changes, and hydrography created opportunities for cladogenesis in the piranhas at different temporal and geographical scales.

BackgroundLeuciscinae is a subfamily belonging to the Cyprinidae fish family that is widely distributed in Circum-Mediterranean region. Many efforts have been carried out to deciphering the evolutionary history of this group. Thus, different biogeographical scenarios have tried to explain the colonization of Europe and Mediterranean area by cyprinids, such as the "north dispersal" or the "Lago Mare dispersal" models. Most recently, Pleistocene glaciations influenced the distribution of leuciscins, especially in North and Central Europe. Weighing up these biogeographical scenarios, this paper constitutes not only the first attempt at deciphering the mitochondrial and nuclear relationships of Mediterranean leuciscins but also a test of biogeographical hypotheses that could have determined the current distribution of Circum-Mediterranean leuciscins.ResultsA total of 4439 characters (mitochondrial + nuclear) from 321 individuals of 176 leuciscine species rendered a well-supported phylogeny, showing fourteen main lineages. Analyses of independent mitochondrial and nuclear markers supported the same main lineages, but basal relationships were not concordant. Moreover, some incongruence was found among independent mitochondrial and nuclear phylogenies. The monophyly of some poorly known genera such as Pseudophoxinus and Petroleuciscus was rejected. Representatives of both genera belong to different evolutionary lineages. Timing of cladogenetic events among the main leuciscine lineages was gained using mitochondrial and all genes data set.ConclusionsAdaptations to a predatory lifestyle or miniaturization have superimposed the morphology of some species. These species have been separated into different genera, which are not supported by a phylogenetic framework. Such is the case of the genera Pseudophoxinus and Petroleuciscus, which real taxonomy is not well known. The diversification of leuciscine lineages has been determined by intense vicariant events following the paleoclimatological and hydrogeological history of Mediterranean region. We propose different colonization models of Mediterranean region during the early Oligocene. Later vicariance events promoted Leuciscinae diversification during Oligocene and Miocene periods. Our data corroborate the presence of leuciscins in North Africa before the Messinian salinity crisis. Indeed, Messinian period appears as a stage of gradually Leuciscinae diversification. The rise of humidity at the beginning of the Pliocene promoted the colonization and posterior isolation of newly established freshwater populations. Finally, Pleistocene glaciations determined the current European distribution of some leuciscine species.

Desmodus rotundus (Chiroptera: Phyllostomidae; Desmodontinae) is the most common vampire bat and has a broad distribution, ranging from southern Mexico to central Chile in the west, and Paraguay and northern Argentina in the east of South America (Koopman 1988). Because of its feeding habit, this bat is considered the main source of rabies transmission to cattle. Although this species has a large spectrum of morphological variability throughout its range, thus far no study has examined the distribution of genetic lineages over its geographic range. Four geographically circumscribed clades ofD. rotundus were described in the Brazilian territory on the basis of mitochondrial sequence analyses: southern Atlantic forest (SAF), northern Atlantic forest (NAF), Pantanal (PAN) and Amazon plus Cerrado (AMC) clade. The differentiation among these clades is strongly supported statistically, although the phylogenetic relationship between them remains uncertain. The extremely high levels of sequence divergence that were found between clades (ranging from 6% to 11%) are the highest ever described for a Neotropical bat species and cannot be explained by female philopatry alone. This indicates that D. rotundus comprises two or more distinct, possibly cryptic species. The biogeographic pattern described for this bat is similar to those described for other bats and terrestrial mammals, suggesting geographical congruence between historical vicariant processes, including likely vicariant events between north and south Atlantic Forest and between the Atlantic Forest and the Amazon. Desmodus rotundus (Chiroptera: Phyllostomidae; Desmodontinae) es el murciélago vampiro más común y presenta una amplia distribución, desde el sur de México hasta el centro de Chile en el oeste, incluyendo Paraguay y el norte de Argentina en el este de América del Sur (Koopman 1988). Debido a sus hábitos alimenticios, este murciélago es considerado el principal transmisor de rabia al ganado. Aunque estas especies tienen un gran espectro de variabilidad morfológica, hasta ahora ninguna investigación ha sido realizada para averiguar la distribución geográfica de los linajes genéticos en un contexto filogeográfico. Utilizándose el secuenciamiento de genes mitocondriales y análisis filogenéticos, cuatro clados geográficamente circunscritos de D. rotundus fueron descritos en territorio brasilero: los de la región Norte de la Floresta Atlántica, la región Sur de la Floresta Atlántica, los de Cerrado y Amazonia, y los de Pantanal. La diferenciación entre esos clados es fuertemente soportada por análisis estadísticos, aunque las relaciones filogenéticas entre ellos no sea muy clara. Los niveles de divergencia observados entre los clados (entre 6% y 11%) son los más altos ya descritos para una especie de murciélago neotropical y no pueden ser explicados solamente por filopatria de hembras. Esto indica que lo que conocemos como D. rotundus es en realidad dos o más especies. El patrón biogeográfico descripto para este murciélago es similar a aquel descripto para otros murciélagos y mamíferos terrestres, sugiriendo una congruencia geográfica entre procesos históricos vicariantes, incluyendo eventos vicariantes entre las Florestas Atlánticas del Norte y Sur y entre la Floresta Atlántica y la Amazonia.

As global medical resources become increasingly scarce, the demand for medicinal plants continues to rise. The growth and metabolism of medicinal plants are closely linked to rhizosphere and endophytic microorganisms. The rhizosphere soil and internal tissues of plants form stable, nutrient-rich ecosystems largely dominated by microbial communities. However, how the rhizosphere and endophytic microbiomes of Fritillaria thunbergii vary across geographically distinct populations, and what ecological processes shape their assembly and functional potential remain largely unexplored. We hypothesized that distinct environmental selection pressures and spatial isolation would differentially shape the assembly of bacterial and fungal communities in bulb and rhizosphere niches, and that core and unique microbial taxa play pivotal roles in shaping ecological network structure. In this study, metabarcoding was employed to investigate the bacterial and fungal communities in the rhizosphere soil and bulbs of F. thunbergii across four populations in China, with the aim of elucidating the biogeographic patterns, assembly mechanisms, and ecological networks of the plant-associated microbiome. The results indicate that both bacterial and fungal communities exhibited significant differences in diversity and composition across the four populations, shaped jointly by geographic isolation and environmental selection. Only a few taxa displayed both cosmopolitan distributions and high abundance, whereas most communities were distinct among ecotypes. Co-occurrence network analysis revealed that core taxa exerted stronger ecological relevance within bacterial and fungal communities compared to other ecotypes, while unique taxa played more pivotal roles in cross-domain networks. Phylogenetic analyses further uncovered microdiverse clades shaped by environmental selection, which may enhance functional resilience and contribute to the overall biogeographic patterns observed. By elucidating the biogeographic patterns and assembly mechanisms of the F. thunbergii microbiome, the study provides a conceptual framework for understanding plant-microbe interactions in medicinal plants and offers insights for the sustainable utilization of microbial resources in traditional medicine.

Recent studies have proposed different biogeographic patterns of intertidal Diaulota and marine littoral Psammostiba along the Pacific coasts of the Northern Hemisphere. To compare the biogeographic patterns of different lineages of aleocharine beetles and explore the recurrent patterns among them, we studied coastal Adota, with a distribution range almost identical to those of Diaulota and Psammostiba. We performed phylogenetic analysis of the marine littoral Adota occurring on the Pacific coasts of the Northern Hemisphere using molecular characters (5188bp: ~1452bp of COI, ~404bp of COII, ~475bp of 16S, ~879bp of 18S, ~973bp of 28S, ~542bp of EF1-α and ~463bp of Wg) to discuss their phylogenetic relationships and biogeographic patterns. The data were analysed using parsimony (PA), Bayesian (BA) and maximum likelihood (ML) methods. The genus Adota and clade A with the same patterns of relationships (A. sinanensis ((A. elongata+A. koreana) (A. magnipennis +A. ushio))), were strongly supported as monophyletic in all analyses. The PA, BA and ML analyses yielded different species relationships in clade B: (A. kamchatkaensis (A. namhae + A. maritima)) in the ML tree using IQ-TREE2, (A. namhae (A. kamchatkaensis +A. maritima)) in the BA and RAxML trees and unresolved polytomy in the PA tree. Our results suggest that the ancestors of Adota were widespread along the East Asian coasts (North and South Korea, Japan, and Kamchatka, Russia). Subsequently, Adota species expanded their range and underwent vicariance between South Korea and Japan and Russia (Kamchatka). Later, another dispersal event occurred from South Korea and Japan to North America and a vicariance event occurred between South Korea and Japan, and North America. Adota have similar biogeographical patterns to Psammostiba, probably because they occupy the same microhabitats and have similar biological characteristics. The findings demonstrate the importance of microhabitats and biological traits in the study of biogeographic patterns of marine coastal insects.