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1. Out of the temperate zone: A phylogenomic test of the biogeographical conservatism hypothesis in a contrarian clade of ants

   https://doi.org/10.1111/jbi.14462  

   Branstetter, Michael G. ; Longino, John T. ; Reyes‐López, Joaquín L. ; Brady, Seán G. ; Schultz, Ted R. ( July 2022 , Journal of Biogeography)

   The standard latitudinal diversity gradient (LDG), in which species richness decreases from equator to pole, is a pervasive pattern observed in most organisms. Some lineages, however, exhibit inverse LDGs. Seemingly problematic, documenting and studying contrarian groups can advance understanding of LDGs generally. Here, we identify one such contrarian clade and use a historical approach to evaluate alternative hypotheses that might explain the group's atypical diversity pattern. We focus on the biogeographical conservatism hypothesis (BCH) and the diversification rate hypothesis (DRH).

   Global.

   Ants (Hymenoptera: Formicidae: Stenammini).

   We examined the shape of the LDG in Stenammini by plotting latitudinal midpoints for all extant, described species. We inferred a robust genome‐scale phylogeny using UCE data. We estimated divergence dates using beast2 and tested several biogeographical models inBioGeoBEARS. To examine diversification rates and test for a correlation between rate and latitude, we used the programs BAMM and STRAPP, respectively.

   Stenammini has a skewed inverse LDG with a richness peak in the northern temperate zone. Phylogenomic analyses revealed five major clades and several instances of non‐monophyly among genera (Goniomma,Aphaenogaster). Stenammini and all its major lineages arose in the northern temperate zone. The tribe originated ~51 Ma during a climatic optimum and then diversified and dispersed southward as global climate cooled. Stenammini invaded the tropics at least seven times, but these events occurred more recently and were not linked with increased diversification. There is evidence for a diversification rate increase in HolarcticAphaenogaster + Messor, but we found no significant correlation between latitude and diversification rate generally.

   Our results largely support the BCH as an explanation for the inverse latitudinal gradient in Stenammini. The clade originated in the Holarctic and likely became more diverse there due to center‐of‐origin, time‐for‐speciation and niche conservatism effects, rather than latitudinal differences in diversification rate.

    

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2. Phylogenetic structure of geographical co‐occurrence among New World Triatominae species, vectors of Chagas disease

   https://doi.org/10.1111/jbi.13810  

   Ceccarelli, Soledad ; Justi, Silvia A. ; Rabinovich, Jorge E. ; Diniz Filho, José Alexandre F. ; Villalobos, Fabricio ( March 2020 , Journal of Biogeography)

   The tropical niche conservatism (TNC) hypothesis is one of the most prominent evolutionary hypotheses that has been supported as an explanation for the diversity gradients of several animal taxa, mainly vertebrates. However, the validity of TNC for less‐known taxa such as disease vectors is not clear. Here, we test predictions of TNC in driving the geographical co‐occurrence among triatomine species, vector insects of Chagas disease. We aim to infer the relative effects of ecological and evolutionary processes in determining triatomine species richness at broad spatial scales.

   America.

   Triatominae (Hemiptera: Reduviidae).

   We gathered distributional, phylogenetic and climatic information for 63 triatomine species. We apply the phylogenetic field (PF) framework based on the phylogenetic structure of species co‐occurrences, considering their climatic preferences. We defined PFs of species by estimating the phylogenetic structure of species co‐occurrence within a focal species’ range. Likewise, climatic conditions within focal species’ ranges were defined as their preferred climates. We applied a spatial‐phylogenetic statistical framework to evaluate geographical variation of species’ co‐occurrence and tested the significance of PFs based on biogeographically informed null models.

   Phylogenetic fields of 17 out of 59 triatomine species showed a trend from overdispersed to clustered, coincident with tropical to subtropical–temperate climate. Triatomines co‐occur with more closely related species in temperate areas and more distantly related species in tropical areas. Temperature seasonality was inversely related to the phylogenetic structure of co‐occurrence within species ranges.

   Geographical co‐occurrence among triatomine species revealed a tropical to subtropical–temperate gradient from overdispersed to clustered PFs and a correspondence between the type of climate in which these species are found and their PFs. Phylogenetic structure within triatomine ranges is explained by their evolutionary history. Our study provides a methodological framework to evaluate the New World triatomine geographical co‐occurrence patterns under a phylogenetic perspective and our results make an important contribution to the understanding of the broad‐scale biodiversity patterns in Triatominae.

    

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3. Global biogeography and diversification of a group of brown seaweeds (Phaeophyceae) driven by clade‐specific evolutionary processes

   https://doi.org/10.1111/jbi.14047  

   Vieira, Christophe ; Steen, Frédérique ; D’hondt, Sofie ; Bafort, Quinten ; Tyberghein, Lennert ; Fernandez‐García, Cindy ; Wysor, Brian ; Tronholm, Ana ; Mattio, Lydiane ; Payri, Claude ; et al ( January 2021 , Journal of Biogeography)

   Historical processes that shaped current diversity patterns of seaweeds remain poorly understood. Using Dictyotales, a globally distributed order of brown seaweeds as a model, we test if historical biogeographical and diversification patterns are comparable across clades. Dictyotales contain some 22 genera, three of which,Dictyota,LobophoraandPadina, are exceptionally diverse. Specifically, we test whether the evolutionary processes that shaped the latitudinal diversity patterns in these clades are in line with the tropical conservatism, out‐of‐the‐tropics or diversification rate hypotheses.

   Global coastal benthic marine environments.

   Dictyotales (Phaeophyceae).

   Species diversity was inferred using DNA‐based species delineation, addressing cryptic diversity and circumventing taxonomic problems. A six‐gene time‐calibrated phylogeny, distribution data of 3,755 specimens and probabilistic modelling of geographical range evolution were used to infer historical biogeographical patterns. The phylogeny was tested against different trait‐dependent models to compare diversification rates for different geographical units as well as different thermal affinities.

   Our results indicate that Dictyotales originated in the Middle Jurassic and reach a current peak of species diversity in the Central Indo‐Pacific. Ancestral range estimation points to a southern hemisphere origin of Dictyotales corresponding to the tropical southern Tethys Sea. Our results demonstrate that diversification rates were generally higher in tropical regions, but increased diversification rates in different clades are driven by different processes. Our results suggest that three major clades underwent a major diversification burst in the early Cenozoic, withDictyotaandPadinaexpanding their distribution into temperate regions whileLobophoraretained a predominantly tropical niche.

   Our results are consistent with both the tropical conservatism hypothesis, in which clades originate and remain in the tropics (Lobophora), and the out‐of‐the‐tropics scenario, where taxa originate and expand towards the temperate regions while preserving their presence in the tropics (Dictyota,Padina).

    

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4. Evolutionary time best explains the latitudinal diversity gradient of living freshwater fish diversity

   https://doi.org/10.1111/geb.13253  

   Miller, Elizabeth Christina ; Román‐Palacios, Cristian ; Tomašových, ed., Adam ( January 2021 , Global Ecology and Biogeography)

   The evolutionary causes of the latitudinal diversity gradient are debated. Hypotheses have ultimately invoked either faster rates of diversification in the tropics or more time for diversification owing to the tropical origins of higher taxa. Here, we perform the first test of the diversification rate and time hypotheses in freshwater ray‐finned fishes, a group comprising nearly a quarter of all living vertebrates.

   Global.

   368–0 Ma.

   Extant freshwater ray‐finned fishes.

   Using a mega‐phylogeny of actinopterygian fishes and a global database of occurrence records, we estimated net diversification rates, the number of colonizations and regional colonization times of co‐occurring species in freshwater drainage basins. We used generalized additive models to test whether these factors were related to latitude. We then compared the influence of diversification rates, numbers of colonizations, colonization times and surface area on species richness, and how these factors are related to each other.

   Although both diversification rates and time were related to richness, time had greater explanatory power and was more strongly related to latitude than diversification rates. Other factors (basin surface area and number of colonizations) also helped to explain richness but were unrelated to latitude. The most diverse freshwater basins of the world (Amazon and Congo rivers) were dominated by lineages having Mesozoic origins. The temperate groups dominant today arrived near the Cretaceous–Palaeogene boundary, leaving comparatively less time to build richness. Diversification rates and colonization times were inversely related: recently colonized basins had the fastest rates, whereas ancient species‐rich faunas had slower rates.

   We concluded that time is the leading driver of latitudinal disparities in richness in freshwater fish faunas. We suggest that the most likely path to building very high species richness is through diversification over long periods of time, rather than through rapid diversification.

    

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5. Conserved ancestral tropical niche but different continental histories explain the latitudinal diversity gradient in brush-footed butterflies

   https://doi.org/10.1038/s41467-021-25906-8  

   Chazot, Nicolas ; Condamine, Fabien L. ; Dudas, Gytis ; Peña, Carlos ; Kodandaramaiah, Ullasa ; Matos-Maraví, Pável ; Aduse-Poku, Kwaku ; Elias, Marianne ; Warren, Andrew D. ; Lohman, David J. ; et al ( September 2021 , Nature Communications)

   The global increase in species richness toward the tropics across continents and taxonomic groups, referred to as the latitudinal diversity gradient, stimulated the formulation of many hypotheses to explain the underlying mechanisms of this pattern. We evaluate several of these hypotheses to explain spatial diversity patterns in a butterfly family, the Nymphalidae, by assessing the contributions of speciation, extinction, and dispersal, and also the extent to which these processes differ among regions at the same latitude. We generate a time-calibrated phylogeny containing 2,866 nymphalid species (~45% of extant diversity). Neither speciation nor extinction rate variations consistently explain the latitudinal diversity gradient among regions because temporal diversification dynamics differ greatly across longitude. The Neotropical diversity results from low extinction rates, not high speciation rates, and biotic interchanges with other regions are rare. Southeast Asia is also characterized by a low speciation rate but, unlike the Neotropics, is the main source of dispersal events through time. Our results suggest that global climate change throughout the Cenozoic, combined with tropical niche conservatism, played a major role in generating the modern latitudinal diversity gradient of nymphalid butterflies.

    

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