Howard Scott Gentry

AbstractPremiseClines—or the geographic sorting of phenotypes across continual space—provide an opportunity to understand the interaction of dispersal, selection, and history in structuring polymorphisms.MethodsIn this study, we combine field‐sampling, genetics, climatic analyses, and machine learning to understand a flower color polymorphism in the wide‐ranging desert annual Encelia farinosa.ResultsWe find evidence for replicated transitions in disk floret color from brown to yellow across spatial scales, with the most prominent cline stretching ~100 km from southwestern United States into México. Because population structure across the cline is minimal, selection is more likely than drift to have an important role in determining cline width.ConclusionsGiven that the cline aligns with a climatic transition but there is no evidence for pollinator preference for flower color, we hypothesize that floret color likely varies as a function of climatic conditions.

Social Impact StatementFor hundreds of years, Agave marmorata plants have been used in the production of alcoholic beverages in Mexico. This species is very important in small‐scale rural economies because it is a large plant, yielding five liters of mezcal. However, the production of these beverages takes place when it reaches its reproductive stage, which takes up to 35 years. Due to its slow maturation and high demand, it is considered an endangered species. Therefore, as a conservation strategy, this study proposes the creation of nurseries, genetic breeding programs, and demographic monitoring of wild populations to counteract the extraction of wild plants and, the conservation of the genetic diversity.Summary Agave marmorata Roezl., is an endemic species distributed in the states of Oaxaca and Puebla, Mexico, and locally is widely used to produce mezcal. We assessed the genomic diversity and differentiation using the RADseq method and 29,101 high‐quality single nucleotide polymorphisms (SNPs) in wild plants and grown under three different management types (cultivated, plants used as live fences, and young plants growing in nurseries). We examined the demographic history and used species distribution modeling to understand the future of A. marmorata under scenarios of climate change. We found high levels of genomic diversity (HS = 0.229) and moderate levels of inbreeding (FIS = 0.106 and Fhat3 = 0.190). The cultivated samples harbored less genetic diversity than the wild plants. Furthermore, we estimated low differentiation between cultivated and wild localities (FST = 0.037). In the wild samples, we identified two main genetic groups, one in the East and another in the West of its distribution area. This genetic structure possibly derived from a population contraction during the Pleistocene (~216,879.75 BP) and the formation of two refugia in small areas with climatic stability. Furthermore, the demographic reconstruction indicated that A. marmorata went through a recent population expansion event, with a large current Ne (Ne = 8,009). The future climate change models indicated contrasting possible changes in its distribution range, from an increase to the reduction of its suitable habitat, differences related to model parametrization, and future levels of CO2 production. We propose conservation measures for the different management types of the species while also considering the biotic and abiotic interactions of Agave marmorata.

Arid and semi-arid areas are highly productive ecosystems that have a great diversity of species, among which grasses stand out. These species have ecological, environmental, and economic importance. The objective was to identify the ecological descriptors of 15 native species of grasses and diversity patterns through multivariate analysis techniques (principal component analysis, PCA, and cluster analysis, CA), in addition to identifying potential distribution areas (current and future) and regions of high and low diversity from 3841 accessions and 21 climatic variables. Among the main results, the extreme values, coefficient of variation, and median for each species could be determined. PCA determined that, with 10 variables, it was possible to explain 54.36% of the variation between the analyzed species. CA resulted in the formation of four statistically significant groups, with specific climatic characteristics. Regarding potential distribution areas and climate change, a reduction in distribution is expected (2050) on most of the current surface, with a possible opportunity zone in the north of the country. Finally, two hotspots (high diversity areas) and four coldspots (low diversity areas) were identified among the analyzed species. These results can be used to create strategies for sustainable use and the conservation of these resources.

Understanding how, and from where, invasive species were introduced is critical for revealing the invasive mechanism, explaining the invasion success, and providing crucial insights for effective management. Here, we combined a phylogeographic approach with ecological niche modeling comparisons to elucidate the introduction mode and source of Nicotiana glauca , a native South American species that is now invasive worldwide. We tested three different scenarios based on the invasion source—random native, restricted native, and bridgehead invasive—considering genetic diversity and climatic niche comparisons among native and invaded areas. We found three genetic lineages geographically and climatically differentiated within the native range. Only one of these genetic groups contained the invasive haplotypes, but showed no climatic niche overlap with any invaded area. Conversely, one invaded area located in western South America, with more genetic diversity than other invaded areas but less than the native range, showed climatic niche overlap with almost all other invaded areas worldwide. These findings indicate that N. glauca first likely invaded the southernmost areas beyond its native range, forming a bridgehead invasive source, from which the species subsequently invaded other regions around the world. Invasiveness would have been fostered by changes in the environmental preferences of the species in the bridgehead area, towards drier, colder and less seasonal climates, becoming the actual source of invasion to areas climatically similar throughout the world. The fine scale resolution analyses combining genetic and climatic approaches within the native range were essential to illuminating the introduction scenario of this invasive species.

Premise: Cacti are characteristic elements of the Neotropical flora and of major interest for biogeographic, evolutionary, and ecological studies. Here we test global biogeographic boundaries for Neotropical Cactaceae using specimen‐based occurrences coupled with data from visual observations, as a means to tackle the known collection biases in the family.MethodsSpecies richness and record density were assessed for preserved specimens and human observations and a bioregional scheme tailored to Cactaceae was produced using the interactive web application Infomap Bioregions based on data from 261,272 point records cleaned through automated and manual steps.Key ResultsWe find that areas in Mexico and southwestern USA, Eastern Brazil and along the Andean region have the greatest density of records and the highest species richness. Human observations complement information from preserved specimens substantially, especially along the Andes. We propose 24 cacti bioregions, among which the most species‐rich are: northern Mexico/southwestern USA, central Mexico, southern central Mexico, Central America, Mexican Pacific coast, central and southern Andes, northwestern Mexico/extreme southwestern USA, southwestern Bolivia, northeastern Brazil, Mexico/Baja California.ConclusionsThe bioregionalization proposed shows biogeographical boundaries specific to cacti, and can thereby aid further evolutionary, biogeographic, and ecological studies by providing a validated framework for further analyses. This classification builds upon, and is distinctive from, other expert‐derived regionalization schemes for other taxa. Our results showcase how observation data, including citizen‐science records, can complement traditional specimen‐based data for biogeographic research, particularly for taxa with specific specimen collection and preservation challenges and those that are threatened or internationally protected.This article is protected by copyright. All rights reserved.

PremiseThe interaction between ecological and evolutionary processes has been recognized as an important factor shaping the evolutionary history of species. Some authors have proposed different ecological and evolutionary hypotheses concerning the relationships between plants and their pollinators, and a special case is the interaction and suspected coevolution among Agave species and their main pollinators, the Leptonycteris bats. Agave species have in general a pollination syndrome compatible with chiropterophily, including floral shape and size, nocturnal nectar production, and nectar quality and sugar concentration. Our goal was to analyze the interaction Agave‐Leptonycteris and its dynamics during three different climate scenarios.MethodsWe modeled the Agave‐Leptonycteris interaction in its spatial and temporal components during Pleistocene, we used Ecological Niche Models (ENMs) and three climate scenarios: Current, Last Glacial Maximum (LGM), and Last InterGlacial (LIG). Further, we analyzed the geographic correlation between 96 Agave species and two the Mexicans Tequila bats, genus Leptonycteris.ResultsWe found that Leptonycteris species interact with different Agave species over their migratory routes. We propose an interaction refuge in Metztitlán and Tehuacán‐Cuicatlán areas, where Agave‐ Leptonycteris interaction has probably remained active. During the non‐migratory season, both bat species consume nectar of almost the same Agave species, suggesting the possibility of a diffuse coevolution among Agave and Leptonycteris bats.ConclusionsWe propose that in the areas related to migratory bat movements, each bat species interacts with different Agave species, whereas in the areas occupied by non‐migrant individuals, both bat species consume nectar of almost the same Agave taxa.This article is protected by copyright. All rights reserved.

Designing multispecies systems with suitable climatic affinity and identifying species' vulnerability under human‐driven climate change are current challenges to achieve successful adaptation of natural systems. To address this problem, we need to (1) identify groups of species with climatic similarity under climate scenarios and (2) identify areas with high conservation value under predicted climate change.To recognize species with similar climatic niche requirements that can be grouped for mixed cropping in Brazil, we employed ecological niche models (ENMs) and Spearman's ρ for overlap. We also used prioritization algorithms to map areas of high conservation value using two Shared Socioeconomic Pathways (SSP2‐4.5 and SSP5‐8.5) to assess mid‐term (2041–2060) and long‐term (2061–2080) climate change impacts.We identified 15 species groups with finer climatic affinities at different times depicted on hierarchical clustering dendrograms, which can be combined into agroecological agroforestry systems. Furthermore, we highlight the climatically suitable areas for these groups of species, thus providing an outlook of where different species will need to be planted over time to be conserved. In addition, we observed that climate change is predicted to modify the spatial association of these groups under different future climate scenarios, causing a mean negative change in species climatic similarity of 9.5% to 13.7% under SSP2‐4.5 scenario and 9.5% to 10.5% under SSP5‐8.5, for 2041–2060 and 2061–2080, respectively.Synthesis and applications. Our findings provide a framework for agroforestry conservation. The groups of species with finer climatic affinities identified and the climatically suitable areas can be combined into agroecological productive systems, and provide an outlook of where different species may be planted over time. In addition, the conservation priority zones displaying high climate stability for each species individually and all at once can be incorporated into Brazil's conservation plans by policymakers to prioritize specific sites. Lastly, we urge policymakers, conservation organizations and donors to promote interventions involving farmers and local communities, since the species' evaluated have proven to maintain landscapes with productive forest fragments and can be conserved in different Brazilian ecosystems.

Mexico harbors ~45% of world’s cacti species richness. Their biogeography and phylogenomics were integrated to elucidate the evolutionary history of the genera Coryphantha, Escobaria, Mammillaria, Mammilloydia, Neolloydia, Ortegocactus, and Pelecyphora (Mammilloid Clade). We analyzed 52 orthologous loci from 142 complete genomes of chloroplast (103 taxa) to generate a cladogram and a chronogram; in the latter, the ancestral distribution was reconstructed with the Dispersal-Extinction-Cladogenesis model. The ancestor of these genera arose ~7 Mya on the Mexican Plateau, from which nine evolutionary lineages evolved. This region was the site of 52% of all the biogeographical processes. The lineages 2, 3 and 6 were responsible for the colonization of the arid southern territories. In the last 4 Mya, the Baja California Peninsula has been a region of prolific evolution, particularly for lineages 8 and 9. Dispersal was the most frequent process and vicariance had relevance in the isolation of cacti distributed in the south of Mexico. The 70 taxa sampled as Mammillaria were distributed in six distinct lineages; one of these presumably corresponded to this genus, which likely had its center of origin in the southern part of the Mexican Plateau. We recommend detailed studies to further determine the taxonomic circumscription of the seven genera.

Mesoamerican mountains are important centers of endemism and diversity of epiphytes. The Sierra Madre of Chiapas in southeastern Mexico is a mountainous region of great ecological interest due to its high biological richness. We present the first checklist of epiphytes for this region based on a compilation of various information sources. In addition, we determined the conservation status for each species based on the Mexican Official Standard (NOM-059-SEMARNAT-2010), endemism based on geopolitical boundaries, spatial completeness with inventory completeness index, richness distribution with range maps, and the relationship between climatic variables (temperature and rainfall) with species richness using generalized additive models. Our dataset includes 9,799 records collected between 1896-2017. Our checklist includes 708 epiphytes within 160 genera and 26 families; the most species-rich family was Orchidaceae (355 species), followed by Bromeliaceae (82) and Polypodiaceae (79). There were 74 species within a category of risk and 59 species considered endemic. Completeness of epiphyte richness suggests that sampling is still largely incomplete, particularly in the lower parts of the mountain system. Species and family range maps show the highest richness at high elevations, while geographically richness increases towards the southeast. Epiphyte richness increases with increased rainfall, although a unimodal pattern was observed along the temperature gradient with a species richness peak between 16-20 C°. The Sierra Madre of Chiapas forms a refuge to more than 40% of all epiphytes reported for Mexico and its existing network of protected areas overlaps with the greatest epiphyte richness.

Paleoclimate reconstructions can provide a window into the environmental conditions in Earth history when atmospheric carbon dioxide concentrations were higher than today. In the eastern USA, paleoclimate reconstructions are sparse, because terrestrial sedimentary deposits are rare. Despite this, the eastern USA has the largest population and population density in North America, and understanding the effects of current and future climate change is of vital importance. Here, we provide terrestrial paleoclimate reconstructions of the eastern USA from Miocene fossil floras. Additionally, we compare proxy paleoclimate reconstructions from the warmest period in the Miocene, the Miocene Climatic Optimum (MCO), to those of an MCO Earth System Model. Reconstructed Miocene temperatures and precipitation north of 35°N are higher than modern. In contrast, south of 35°N, temperatures and precipitation are similar to today, suggesting a poleward amplification effect in eastern North America. Reconstructed Miocene rainfall seasonality was predominantly higher than modern, regardless of latitude, indicating greater variability in intra-annual moisture transport. Reconstructed climates are almost uniformly in the temperate seasonal forest biome, but heterogeneity of specific forest types is evident. Reconstructed Miocene terrestrial temperatures from the eastern USA are lower than modeled temperatures and coeval Atlantic sea surface temperatures. However, reconstructed rainfall is consistent with modeled rainfall. Our results show that during the Miocene, climate was most different from modern in the northeastern states, and may suggest a drastic reduction in the meridional temperature gradient along the North American east coast compared to today.