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Open Access Publications from the University of California

Frontiers of Biogeography

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Frontiers of Biogeography (FoB) is the scientific journal of the International Biogeography Society (IBS,, a not-for-profit organization dedicated to promotion of and public understanding of the biogeographical sciences.  IBS launched FoB to provide an independent forum for biogeographical science, with the academic standards expected of a journal operated by and for an academic society.

Issue cover
Ceiba glaziovii (Kuntze) K. Schum. showing the exuberance of its aculeate trunk in Bahia, Brazil. Ceiba Mill. is one of the most iconic inhabitants of the threatened Neotropical seasonally dry tropical forests (SDTF). In this issue, Pezzini and colleagues explore the patterns of species age, monophyly, ecological and geographic structure, through a well-sampled phylogeny for the genus. Photo by Flávia Pezzini.

Research Articles

The EarthLife Consortium API: an extensible, open-source service for accessing fossil data and taxonomies from multiple community paleodata resources

Paleobiologists and paleoecologists interested in studying biodiversity dynamics over broad spatial and temporal scales have built multiple community-curated data resources, each emphasizing a particular spatial domain, timescale, or taxonomic group(s). This multiplicity of data resources is understandable, given the enormous diversity of life across Earth's history, but creates a barrier to achieving a truly global understanding of the diversity and distribution of life across time. Here we present the Earth Life Consortium Application Programming Interface (ELC API), a lightweight data service designed to search and retrieve fossil occurrence and taxonomic information from across multiple paleobiological resources. Key endpoints include Occurrences (returns spatiotemporal locations of fossils for selected taxa), Locales (returns information about sites with fossil data), References (returns bibliographic information), and Taxonomy (returns names of subtaxa associated with selected taxa). Data objects are returned as JSON or CSV format. The ELC API supports tectonic-driven shifts in geographic position back to 580 Ma using services from Macrostrat and GPlates. The ELC API has been implemented first for the Paleobiology Database and Neotoma Paleoecology Database, with a test extension to the Strategic Environmental Archaeology Database. The ELC API is designed to be readily extensible to other paleobiological data resources, with all endpoints fully documented and following open-source standards (e.g., Swagger, OGC). The broader goal is to help build an interlinked and federated ecosystem of paleobiological and paleoenvironmental data resources, which together provide paleobiologists, macroecologists, biogeographers, and other interested scientists with full coverage of the diversity and distribution of life across time.

Phylogeny and biogeography of Ceiba Mill. (Malvaceae, Bombacoideae)

The Neotropics is the most species-rich area in the world, and the mechanisms that generated and maintain its biodiversity are still debated. This paper contributes to the debate by investigating the evolutionary and biogeographic history of the genus Ceiba Mill. (Malvaceae, Bombacoideae). Ceiba comprises 18 mostly Neotropical species, largely endemic to two major biomes, seasonally dry tropical forests (SDTFs) and rain forests. Its species are among the most characteristic elements of Neotropical SDTF, one of the most threatened biomes in the tropics. Phylogenetic analyses of DNA sequence data (from the nuclear ribosomal internal transcribed spacers [nrITS] for 30 accessions representing 14 species of Ceiba) recovered the genus as monophyletic. The phylogeny showed geographic and ecological structure in three main clades: (i) a rain forest lineage of nine accessions of C. pentandra sister to the remaining species; (ii) a highly supported clade composed of C. schottii and C. aesculifolia from Central American and Mexican SDTF, plus two accessions of C. samauma from semi-humid, inter Andean valleys in Peru; and (iii) a highly supported South American SDTF clade including 10 species showing little sequence variation. Within this South American SDTF clade, no species represented by multiple accessions were resolved as monophyletic. We demonstrate that the patterns of species age, monophyly, and geographic structure previously reported for SDTF species within the Leguminosae family are not shared by Ceiba, suggesting that further phylogenetic studies of unrelated groups are required to understand general patterns.

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Limnological response to climatic changes in western Amazonia over the last millennium

The Little Ice Age (LIA - A.D. 1400 to 1820, 550 to 130 cal yr BP) was a significant worldwide climatic fluctuation, yet little is known about its impact on the ecology of Amazonia or its human inhabitants. Using organic geochemistry and diatoms, we investigate the limnological impact of this event in an Amazonian record spanning the last 760 years. The sedimentary record is from Lake Pata (Lagoa da Pata), which lies on the Hill of Six Lakes (Morro dos Seis Lagos), in the wettest section of the western Brazilian Amazonia. We found that many of the diatom taxa recovered from this remote site are either morphotypes of known species or species new to science. Eunotia and Frustulia dominated our fossil diatom assemblage over time, indicating oligotrophic waters of low pH. The limnological characteristics of this pristine system changed very little over the last millennium, except for a slight intensification of precipitation indicated by the increase in Aulacoseira granulata abundances, in C/N ratios, and in sedimentation rates. This phase lasted from 1190 to 1400 A.D. (760 to 550 cal yr BP). Although occurring before the onset of LIA, the observed change matched increases in precipitation observed in Venezuelan glaciers and Peruvian speleothems. We conclude that although the changes in precipitation detected in our lake match the timing of precipitation increase in some South American records, the event was shorter and its effects in this region of Amazonia were mild compared with other regional records. Our paleolimnological data provide additional insights into the interpretation of a remarkably stable fossil pollen record, in that the highest variance in vegetation occurred over the last millennium. Because Lake Pata has no human influence, part of its value is in providing a reference, with which variability in other settings that do have a human history, can be compared.

Land snails on islands: building a global inventory

Land snails are one of the most diverse groups of terrestrial animals and are commonly used as model organisms in ecology, biogeography and conservation biology. Despite being poor dispersers, they form crucial components of island faunas and exhibit high percentages of endemism. Insular land snails are also among the most threatened animals on Earth, already having suffered extensive human-caused extinctions. However, current estimates of global insular land snail diversity are based on sporadic records published at the scale of individual islands and/or archipelagos. To tackle this shortfall, we herein present the major features of a global inventory of island snails. We recovered full species lists from existing literature and available species checklists for 727 islands across the globe and collated a database which currently includes the occurrence of 11,139 species, that is approximately 48% of all known land snail species (of which there are an estimated 23,000). Seventy-five percent of the species are single-island endemics, underlining the exceptional nature of islands as global biodiversity hotspots. Overall, our attempt is one of few to examine insular invertebrate diversity at coarser scales and a crucial step to the study of global patterns in island biodiversity.

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Biogeographic patterns of blood parasitism in the Aegean Wall Lizard across the cycladic islands

The biogeography of host-parasite dynamics is an area that has received little attention in studies of island ecology. While a few studies have shed insight on patterns of parasitism in insular host populations, more empirical evidence is needed to ascertain how isolation impacts parasites. Biogeography generally theorizes that the physical size of islands and the duration of each island’s isolation can be driving geographic factors controlling species interactions and populations dynamics. To test this, we assessed the effect of island structure and population isolation on the endemic insular lizard Podarcis erhardii and its native hemogregarine parasite (Apicomplexa: Adeleorina) in the Cyclades (Aegean Sea). We analyzed the relationships of prevalence and parasitemia of hemogregarine infection with several factors concerning the island (size, time of isolation, spatial isolation, population density) and host (body size) levels using regression and structural equation models, respectively. Regressions indicate that islands with greater host density and islands which have been isolated for shorter timespans tend to have higher hemogregarine prevalences; structural equation models suggest a similar pattern for parasitemia. We hypothesize this may be driven by insular density compensation. Hosts on islands that are more temporally and spatially isolated also tend to have higher prevalence and parasitemia of hemogregarines. Our results indicate that island area, island isolation, and host population density are likely to be significant drivers of changes in host-parasite interactions in fragmented populations.

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Non-overlapping climatic niches and biogeographic barriers explain disjunct distributions of continental Urania moths

Larvae of Urania moths feed exclusively on Omphalea plants, which are widely distributed in the Neotropics. However, the distributions of the two Urania species in this region are disjunct. This distributional pattern could derive from the presence of the Andes, but it could also be related to differences in ecological niches, the presence of negative interactions, or the absence of conditions that can only be observed at a habitat level. We tested whether differences in the ecological niches of continental Urania moths play a role in their disjunct distribution. Using species records and climatic variables, we characterized the ecological niches of Urania moths and their host plants and analyzed the overlap of the moths' niches. Using ecoregions as a proxy of habitat-level environmental conditions, we explored the role of host plant availability on the moth distributions. Suitable conditions for the species were widespread, with a lack of suitability mostly restricted to the Andean highlands. The two moth distributions were closely related to that of their host plants. There was medium-high overlap of niche models when available conditions were considered; however, niche overlap was not found to be statistically significant. Our results corroborate the barrier effect of the Andes on the dispersal of these moths, but they also show that niche differences contribute to the disjunct distributions of U. fulgens and U. leilus. Furthermore, other non-climatic factors appear to play a crucial role in the disjunction of the species ranges in areas where overlapping suitable conditions are continuous. Our findings support speciation in Urania moths as allopatric and indicate that their disjunct distributions can be attributed to multiple factors. Other studies exploring the causes of similar distributional patterns should consider that a single factor may not be enough to explain such patterns.

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Annual precipitation drives fire occurrence across sub-humid and semi-arid ecological gradients

Fire is an integral part of semiarid to moderately humid ecosystem dynamics in North America. The biogeographical settings in which fires readily occur are affected by global processes like climate change, as well as local and regional characteristics such as terrain, proximity to human infrastructure, and vegetation structure. Increasing numbers and severity of fires today requires high-resolution and accurate predictions of fire probability. Species distribution models (SDM) allow researchers to identify environmental predictors of fire and depict the probability of fire occurrence. We applied a Maximum Entropy (Maxent) SDM to identify fire predictors and fire risk across a broad biogeographic humid to semi-arid climate gradient within the state of Texas. We used 15 years (2001-2016) of remotely sensed fire occurrence data, along with 13 biophysical variables representing climate, terrain, human activity, and landcover to generate multiple models. Annual precipitation was the primary predictor of fire occurrence, followed by elevation and landcover. After projecting fire probability onto three climate scenarios, we found moderate change in fire distribution. Humid and sub-humid areas had higher probabilities of fire occurrence while arid regions had lower probabilities under those scenarios. Overall, the linkage between fire occurrence and annual precipitation suggests that climate-driven fire probabilities will be variable under projected future climates.

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Revealing receiver bias in the communication of mapped biodiversity patterns

Researchers often communicate knowledge about biodiversity, especially information about where species are likely to be found, through maps. However, readers do not necessarily interpret such maps in the way the authors intend. We assessed undergraduate students' interpretations of mapped biodiversity data with a mixed-method approach: a survey instrument was developed using writing and focus groups, then delivered to students enrolled in introductory biology courses at the University of Florida in the United States. Surveyed participants (N = 195) were presented with sets of maps for the Palamedes Swallowtail butterfly, Papilio palamedes, with three data visualization methods: point occurrences, expert-assessed range, and correlative distribution model results (distributional models were shown at high and low resolutions). Map interpretations were assessed by asking participants to rate the likelihood of finding a Palamedes Swallowtail at various point on each map and how confident they were in the information the map presented. They were also asked which map type they would most likely use to find a Palamedes Swallowtail. For distributional model maps, the effect of resolution on interpretation was assessed by asking participants to rate the perceived accuracy of each map, as well as their confidence in the data being presented. Participants most trusted in data provided via point maps compared to range and distributional model maps, and trusted point maps most among the three map types. For distribution maps, participants felt more certain in data presented to them via higher-resolution maps and interpreted them as being more accurate. This preference was especially pronounced for participants studying Science, Technology, Engineering, and Mathematics (STEM) fields compared to their non-STEM peers. Our findings suggest biodiversity researchers need to carefully consider symbol choice and resolution when transmitting information about species distributions.

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Taxonomic hypotheses and the biogeography of speciation in the Tiger Whiptail complex (Aspidoscelis tigris: Squamata, Teiidae)

Biodiversity in southwestern North America has a complex biogeographic history involving tectonism interspersed with climatic fluctuations. This yields a contemporary pattern replete with historic idiosyncrasies often difficult to interpret when viewed from through the lens of modern ecology. The Aspidoscelis tigris (Tiger Whiptail) complex (Squamata: Teiidae) is one such group in which taxonomic boundaries have been confounded by a series of complex biogeographic processes that have defined the evolution of the clade. To clarify this situation, we first generated multiple taxonomic hypotheses, which were subsequently tested using mitochondrial DNA sequences (ATPase 8 and 6) evaluated across 239 individuals representing five continental members of this complex. We then evaluated the manner by which our models parsed phylogenetic and biogeographic patterns. We found considerable variation among species ‘hypotheses,’ which we interpret as reflecting inflated levels of inter-population genetic divergence caused by historical demographic expansion and contraction cycles. Inter-specific boundaries with A. marmoratus juxtaposed topographically with the Cochise Filter Barrier that separates Sonoran and Chihuahuan deserts (interpreted herein as an example of ‘soft’ allopatry). Patterns of genetic divergence were consistent across the Cochise Filter Barrier, regardless of sample proximity. Surprisingly, this also held true for intraspecific comparisons that spanned the Colorado River. These in turn suggest geomorphic processes as a driver of speciation in the A. tigris complex, with intraspecific units governed by local demographic processes.

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Opinions, Perspectives & Reviews

Advances in conservation biogeography: towards protected area effectiveness under anthropogenic threats

This study endorses the main findings of a PhD thesis (Hoffmann 2020) and the manuscripts included intend to advance the success of protected areas in biodiversity conservation mediated through effective and efficient protected area management. The manuscripts provide missing scientific evaluations that modern conservation planning over large geographical extents requires: the comprehensive quantification of species diversity within and between protected areas; the development and application of efficient and effective in-situ monitoring and remote sensing of species diversity; and the assessment of anthropogenic climate change threats to protected areas. Moreover, the manuscripts aim at spreading conservation-minded data and knowledge by means of publishing open-access papers, open-source software and open data. This thesis synopsis is to stimulate a growing scientific and public debate on the effectiveness of protected areas and nature conservation under anthropogenic threats, which is necessary to stop nature’s decline and thus guarantee a sustainable future for the welfare of generations to come.

Conservation biogeography of the terrestrial mammals in Iran: diversity patterns, and vulnerability to climate change and extinction

Under the framework of a “conservation biogeography” approach, initially, I reviewed and updated the taxonomy and distribution of the rich but understudied mammalian diversity of Iran. This data then formed the basis for the biogeographical regionalization of this complex transitional area using hierarchical clustering and infomap network methods. I used linear models to explore the correlates of extinction risk for this threatened mammalian fauna. Functional grouping of target species was used to assess their vulnerability to the magnitude and velocity of climate change impacts. Both clustering and network methods successfully illuminated the intricate biogeographic patterns, while the network detected many more small bioregions, including two transition zones. The extinction risk analyses revealed that human activities, such as hunting and persecuting (direct impacts) played a major role in the decline of these taxa, as opposed to minor effect of indirect and instrinsic and extrinsic factors. The magnitude and velocity of climate change impacts varied significantly between functional groups, with the highest risk of exposure to extreme climates in large and threatened species occurring in lowlands. This study provides a foundation for future biogeographic, systematics and ecological studies of Iranian mammals while simultaneously adding to the limited available information on the bioregionalization at regional scales. And it highlights the importance of incorporating threats in extinction risk models and functional trait information in climate change impact assessments.

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Book Reviews

How the fraying fabric was woven: a pocket guide to the changing world

The Very Short Introductions series, which now includes Mark Lomolino’s new book Biogeography, aims to give “anyone ... a stimulating and accessible way into a new subject” (p. ii). In such an holistic discipline as biogeography, in such a short book, finding the hooks to engage a diverse audience and represent the field seems like an impossible task. But having co- authored a, if not the discipline’s preeminent, full-size biogeography text (Lomolino et al. 2016), probably few are as well positioned as Lomolino to distil biogeography’s essence.

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