Diversity and Distributional Patterns of Neotropical Freshwater Copepods (Calanoida: Diaptomidae)

The distributional patterns and diversity of the diaptomid calanoid copepods were analysed to assess the faunistic affinity of North and South America with respect to Mexico and Central America. In the Neotropical region, the most speciose genera of Diaptomidae are Leptodiaptomus and Mastigodiaptomus. The former genus is a Nearctic form, and Mastigodiaptomus is Neotropical. Based on the current distribution of their diversity, it is probable that these genera radiated into Mexico and Central America from North America and the insular Caribbean, respectively. Arctodiaptomus dorsalis is a primarily Palaearctic taxon, it is widely distributed between North and Central America. This species probably radiated in the Americas as a Tethyan derivate. Prionodiaptomus is the only member of the highly diverse South American diaptomid fauna that has expanded beyond the subcontinent. Despite the high diversity present in South America, its influence in Mexico and Central America appears to be weak; this is probably a consequence of the geologically recent union of the two main subcontinental landmasses. Mexico shares 33% of its species with NA, and no species are shared between NA and SA. For the Diaptomidae, the Nearctic influence is strongest in Mexico. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

CHROMOSOME NUMBERS IN CUPHEA (LYTHRACEAE): NEW COUNTS AND A SUMMARY

The American genus Cuphea with ca. 260 species is extremely diverse with respect to chromosome number. Counts are now available for 78 species and/or varieties, or 29% of the genus. Included in this study are first reports for 15 taxa from Brazil, Cuba, Dominican Republic, Mexico, and Venezuela. Twenty-two different numbers are known for the genus, ranging from n = 6 to n = 54. The most common number in the primary center of species diversity in Brazil is n = 8, which is regarded as the base number of the genus. Two numbers are most common in the secondary center in Mexico, n = 10 and n = 12. Species with n = 14 or higher are considered to be of polyploid origin. Polyploids comprise 46% of the total species counted and appear in 9 of the 11 sections for which chromosome numbers have been reported. Aneuploid species comprise ca. 25% of the genus and are known from 7 of the 11 sections. The two subgenera are not characterized by different chromosome numbers or sequences of numbers. None of the 14 sections are circumscribed by a single chromosome number. Morphological and ecological variability in widespread, weedy species is correlated with differing chromosome numbers in some species whereas in others the chromosome number is stable. Summary of chromosome numbers by taxonomic section is presented. Section Euandra, centered in eastern Brazil, and the largest section of the genus, appears to be chromosomally most diverse. In section Trispermum, characterized by difficult, variable species with intermediate forms, two of the four species studied have polyploid races. Section Heterodon, endemic to Mexico and Central America and comprising most of the annual species of the genus, is best known chromosomally. Chromosome numbers have been counted for 25 of 28 species, and 12 different numbers are reported. The most advanced sections, Melvilla and Diploptychia, with numerous species occurring at higher altitudes, are characterized by high polyploids. Apomictic species occur in sect. Diploptycia. The cytoevolution of Cuphea is complex with frequent polyploid and aneuploid events apparently playing a significant role in speciation in both centers of diversity.     

Evolutionary ecology of Agave: distribution patterns,phylogeny, and coevolution (an homage to Howard S. Gentry)

With more than 200 species, the genus Agave is one of the most interesting and complex groups of plants in the world, considering for instance its great diversity and adaptations. The adaptations include the production of a single, massive inflorescence (the largest among plants) where after growing for many years, sometimes more than 30, the rosette dies shortly afterward, and the remarkable coevolution with their main pollinators, nectarivorous bats, in particular of the genus Leptonycteris. The physiological adaptations of Agave species include a photosynthetic metabolism that allows efficient use of water and a large degree of succulence, helping to store water and resources for their massive flowering event. Ecologically, the agaves are keystone species on which numerous animal species depend for their subsistence due to the large amounts of pollen and nectar they produce, that support many pollinators, including bats, perching birds, hummingbirds, moths, and bees. Moreover, in many regions of Mexico and in the southwestern United States, agaves are dominant species. We describe the contributions of H. S. Gentry to the understanding of agaves and review recent advances on the study of the ecology and evolution of the genus. We analyze the present and inferred past distribution patterns of different species in the genus, describing differences in their climatic niche and adaptations to dry conditions. We interpret these patterns using molecular clock data and phylogenetic analyses and information of their coevolving pollinators and from phylogeographic, morphological, and ecological studies and discuss the prospects for their future conservation and management.     

The Opuntia (Cactaceae) and Dactylopius (Hemiptera: Dactylopiidae) in Mexico: a historical perspective of use, interaction and distribution

A historical perspective on the use and production of species of Dactylopius (Hemipetera: Dactylopiidae) and Opuntia (Cactaceae: Opuntioidae), information on their origin, diversity and distribution in Mexico are reviewed, and aspects of their conservation are discussed. The use and exploitation of both genera are part of Mexican cultures since prehistory. Opuntia species were among the main components of human diet during pre-agricultural times. Cochineal was used and probably cultivated at least from the Tenth century. During the colonial period, cochineal generated significant benefits to the Spaniard colonizers and Mexico was the world’s first producer of insects and dyes until the mid Nineteenth century. Currently, Mexico is the main producer of Opuntia cladodes and prickly pear, but cochineal cultivation is marginal and only maintained in traditional indigenous systems. Mexico is one of the main areas of diversity of Opuntia, having 83–104 out of nearly 200 species worldwide. More than 50 species are used mainly as food, fodder and medicine and 20 species are cultivated with different degrees of domestication. The genus Dactylopius includes nine species, with five of them naturally occurring in Mexico. Only D. coccus has been cultivated and domesticated but other wild species have been used throughout history. Arid and semiarid areas of Mexico are among the most important reservoirs of biological diversity for both genera, particularly for D. coccus. Specific measures for protection of such biodiversity and generic resources are required. Strategies for in situ conservation combined with re-established use and cochineal production may enhance conservation policies.     

Neurospora in temperate forests of western North America

The fungal genus Neurospora has a distinguished history as a laboratory model in genetics and biochemistry. The most recent milestone in this history has been the sequencing of the genome of the best known species, N. crassa. The hope and promise of a complete genome sequence is a full understanding of the biology of the organism. Full understanding cannot be achieved, however, in the absence of fundamental knowledge of natural history. We report that species of Neurospora, heretofore thought to occur mainly in moist tropical and subtropical regions, are common primary colonizers of trees and shrubs killed by forest fires in western North America, in regions that are often cold and dry. Surveys in 36 forest-fire sites from New Mexico to Alaska yielded more than 500 cultures, 95% of which were the rarely collected N. discreta. Initial characterization of genotypes both within a site and on a single tree showed diversity consistent with sexual reproduction of N. discreta. These discoveries fill important gaps in knowledge of the distribution of members of the genus on both large and small spatial scales and provide the framework for future studies in new regions and microhabitats. The overall result is that population biology and genetics now can be combined, placing the genus Neurospora in a unique position to expand its role in experimental biology as a useful model organism for ecology, population genetics and evolution.     

A new species of Leptodiaptomus (Copepoda, Diaptomidae) from Northwestern Mexico with comments on the distribution of the genus

A new species of the freshwater planktonic copepod genus Leptodiaptomus is described for a small pond in Northwestern Mexico. Leptodiaptomus dodsoni n. sp. can be easily distinguished mainly by the presence of an unusually large sinusoid spine on male antennular segment 13, and by the features of the fifth legs of both sexes. This genus is known to be distributed mainly in North America with 19 recognized species. Of these, six ocur in Mexico, and the new species seems to be closely related to most of them. It is probable that this group of species (including the new one) represents the southwards radiation of the genus from North America. Compared to the Caribbean and South American, the North American influence seems to be the most relevant for diaptomid copepods in Mexico. At least two Mexican species of Leptodiaptomus, including L.dodsoni, are restricted in distributional range to high-altitude temporal ponds, and both could be considered endemics.      

Evaluating hypotheses on the origin and diversification of the ringneck snake Diadophis punctatus (Colubridae: Dipsadinae)

Close affinities recognized between taxa in Mexico and the contiguous USA have led to a variety of biogeographical scenarios. One such hypothesis suggests that species that occur in both countries have an origin in central Mexico followed by dispersal into the USA. This study expands upon previous phylogeographical work of the ringneck snake Diadophis punctatus by incorporating new data from previously unsampled areas appropriate to critically assess hypotheses regarding a Mexican origin for this species. Maximum likelihood and maximum parsimony analyses inferred a derived position for the lineage from southern Mexico with constraint tests for alternate evolutionary hypotheses resulting in significantly worse likelihood values. Ancestral area reconstructions inferred an origin for D. punctatus in the south‐eastern USA followed by a south‐east to north‐east then westward directionality of historical migration. The position within the phylogeny and date estimate for the south‐western + Mexico clade suggests a recent invasion into central Mexico with expansion into the Nearctic/Neotropic transition zone. The extensive lineage diversity inferred from the mtDNA suggests that the genus is a complex of cryptic species whose conservational status should be re‐evaluated on both the national and regional levels. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 629–640.     

Erratum to: Phylogeny and biogeography of the genus Stevia (Asteraceae: Eupatorieae): an example of diversification in the Asteraceae in the new world

The genus Stevia comprises approximately 200 species, which are distributed in North and South America, and are representative of the species diversity of the Asteraceae in the New World. We reconstructed the phylogenetic relationships using sequences of ITS and cpDNA and estimated the divergence times of the major clade of this genus. Our results suggested that Stevia originated in Mexico 7.0–7.3 million years ago (Mya). Two large clades, one with shrub species and another with herb species, were separated at about 6.6 Mya. The phylogenetic reconstruction suggested that an ancestor of Stevia was a small shrub in temperate pine–oak forests and the evolutionary change from a shrub state to a herb state occurred only once. A Brazilian clade was nested in a Mexican herb clade, and its origin was estimated to be 5.2 Mya, suggesting that the migration from North America to South America occurred after the formation of the Isthmus of Panama. The species diversity in Mexico appears to reflect the habitat diversity within the temperate pine–oak forest zone. The presence of many conspecific diploid–polyploid clades in the phylogenetic tree reflects the high frequency of polyploidization among the perennial Stevia species.

     

The phylogenetics of Desmognathine salamander populations across the southern Appalachians

Salamanders in the genus Desmognathus (Caudata: Plethodontidae) are distributed along an aquatic to terrestrial habitat gradient in the southern Appalachian Mountains. The spatial distribution of species is believed to have formed as aquatic ancestors displaced lineages by competition and predatory interactions into less optimal terrestrial habitats. Aquatic and terrestrial species may also display different patterns of genetic diversity due to the differing likelihood of gene flow via aquatic corridors. To determine whether phylogenetic patterns were consistent with these hypotheses, we sequenced portions of the cytochrome oxidase I and 12S rRNA genes of the mitochondrial genome from 96 individuals belonging to 10 species in the genus Desmognathus. In addition, we combined our dataset with an earlier published dataset for the 12S rRNA genes. The order of species divergence is consistent with aquatic ancestors having displaced taxa into more terrestrial habitats, but the major lineages within the genus Desmognathus arose suddenly, and therefore, the specific sequence of events is not well resolved. The phylogenetic analyses among species suggest that direct-development and a terrestrial lifestyle are ancestral in the genus Desmognathus, but the degree of adult terrestriallity is labile, with some species having re-invaded terrestrial habitats. We present evidence of a clade of Desmognathus quadramaculatus from North Carolina that is distinct from the D. quadramaculatus/Desmognathus marmoratus clade. Within species, estimates of Tajima's D and Fu and Li's statistics suggest the species experienced population expansions at different times in the past. Current levels of sequence diversity in northern populations, therefore, reflect different arrival times, and hence, differences in the opportunity for among population divergence. The recent arrival of most species over large portions of their geographic ranges suggests that most extant communities have been assembled, a posteriori, by the recent assortment of species along the aquatic to terrestrial gradient according to their ecologies.     

Cryptic biodiversity and phylogeographical patterns in a snapping shrimp species complex

Recent investigations suggest that marine biodiversity may be much higher than earlier estimates, and an important hidden source of diversity in marine systems is the phenomenon of cryptic species complexes. Such complexes are informative models for research into the evolutionary processes that govern species compositions of marine fauna. The snapping shrimp genera Alpheus and Synalpheus are known to harbour large numbers of cryptic species; here, I characterize the genetic structure of the Alpheus armillatus species complex in the northern Caribbean, west Atlantic, and Gulf of Mexico using mitochondrial and nuclear sequence data. Over this geographical region, the complex harbours at least three lineages that are probable reproductively isolated species; all major lineages diverged subsequent to the close of the Isthmus of Panama. Only one lineage was present in the Gulf of Mexico, whereas outside the Gulf of Mexico there was no clear tendency for lineage dominance by geographical region, as most sites were populated by shrimp from at least two lineages. However, within each lineage, there was strong evidence of population genetic differentiation between geographical regions. All lineages showed strong signals of demographic expansion, and one lineage showed sharply reduced genetic diversity, suggestive of past population bottlenecks or recently founded populations with low gene flow from other sites. These results show that evolutionary processes leading to divergence and speciation have been common and recent in the snapping shrimp, and suggest that connectivity among shrimp populations may be limited.     

Genetic diversity and phylogeographic analysis of Pinus leiophylla: a post-glacial range expansion

Aim Mexico is a centre of diversity for species of the genus Pinus, most of which have restricted geographical distributions. An exception is Pinus leiophylla Schiede and Deppe, which is widely distributed throughout most of Mexico’s mountainous regions. We attempt to reconstruct the phylogeographic history of this species, in order to determine if its current broad distribution is associated with major events of environmental change that occurred during the Quaternary. Location Coniferous forests in Sierra Madre Occidental, Eje Volcánico Transversal and Sierra Montañosa del Norte de Oaxaca, Mexico. Methods A total of 323 individuals of both P. leiophylla var. leiophylla and P. leiophylla var. chihuahuana sampled from 22 populations were screened for variation at six paternally inherited chloroplast DNA microsatellite markers (cpSSR). In addition to haplotypic diversity estimates and neutrality tests, the following clustering methods were employed: principal components analysis (PCA), analysis of molecular variance (AMOVA), spatial analysis of molecular variance (SAMOVA), haplotype network and a technique similar to Croizat’s panbiogeographical method of individual and generalized tracks. Results The combination of mutations at the six microsatellites yielded a total of 92 different haplotypes. The percentage of shared haplotypes between varieties (P. leiophylla var. leiophylla and P. leiophylla var. chihuahuana) was only 2.2%. The average haplotypic diversity for the species was H = 0.760. PCA and SAMOVA indicate the presence of four main genetic clusters. The estimated divergence time between the two most frequent haplotypes was between 75,000 and 110,000 years. Significantly large negative F_s values suggest that most of the sampled populations are currently expanding. Individual and generalized tracks identified three potential zones that may have harboured ancestral populations of P. leiophylla and from which the expansion of this species started, as well as two secondary contact zones between the two varieties. Main conclusions The results indicate that one of the three potential areas hypothesized to have harboured ancestral populations of P. leiophylla may be related to the origin of P. leiophylla var. chihuahuana, while the other two may be related to the origin of P. leiophylla var. leiophylla. The current broad distribution of P. leiophylla is probably associated with its strong colonization ability.     

Genetic Structure of the Carnivorous Plant Pinguicula moranensis (Lentibulariaceae) on the Transvolcanic Mexican Belt

Most species of Pinguicula present a montane distribution with populations located at high altitudes. In this context, we proposed that populations of Pinguicula species could be genetically differentiated even at a local scale. This study supported that prediction, as a RAPD-based analysis of molecular variance revealed a high degree of genetic structure (Φ (st) = 0.157, P = 0.001) and low gene flow (Nm = 1.0) among four central populations of Pinguicula moranensis in Mexico, with a maximum geographic separation of about 140 km. The four populations also exhibited high levels of genetic diversity (mean Nei's genetic diversity = 0.3716; % polymorphism = 95.45%). The evolutionary implications of the genetic structure found in P. moranensis for other species in the genus are discussed in the context of the naturally fragmented distribution and a set of life history traits shared by most Pinguicula species that could promote geographic isolation and limited gene flow.     

Phylogeny, diversity, and species delimitation of the North American Round-Nosed Minnows (Teleostei: Dionda), as inferred from mitochondrial and nuclear DNA sequences

Accurate delimitation of species is a critical first step in protecting biodiversity. Detection of distinct species is especially important for groups of organisms that inhabit sensitive environments subject to recent degradation, such as creeks, springs, and rivers in arid or semi-desert regions. The genus Dionda currently includes six recognized and described species of minnows that live in clear springs and spring-fed creeks of Texas, New Mexico (USA), and northern Mexico, but the boundaries, delimitation, and characterization of species in this genus have not been examined rigorously. The habitats of some of the species in this genus are rapidly deteriorating, and many local populations of Dionda have been extirpated. Considering the increasing concerns over degradation of their habitat, and pending a more detailed morphological revision of the genus, we undertook a molecular survey based on four DNA regions to examine variation over the range of the genus, test species boundaries, and infer phylogenetic relationships within Dionda. Based on analyses of two mitochondrial (cytb and D-loop) and two nuclear (Rag1 and S7) DNA regions from specimens collected throughout the range of Dionda, we identified 12 distinct species in the genus. Formerly synonymized names are available for two of these species, and four other species remain undescribed. We also redefine the known range of six species. The limited distribution of several of the species, coupled with widespread habitat degradation, suggests that many of the species in this genus should be targets for conservation and recovery efforts.     

Assessment of littoral algal diversity from the northern Gulf of Mexico using environmental DNA metabarcoding

Traditional methods for algal biodiversity monitoring are costly and time inefficient because they rely on high‐level taxonomic expertise to address species identity problems involving phenotypic plasticity and morphological convergence. These problems are exacerbated in regions such as the Gulf of Mexico, that has a limited history of phycological exploration, but that are economically important or threatened by numerous anthropogenic stressors. Given the high pace of disturbance to natural systems, there is a critical need for expedient and cost‐effective tools for the study of benthic algal communities. Here we document the use of environmental DNA metabarcoding, using the partial LSU rDNA and 23S rDNA plastid molecular markers, to elucidate littoral algal diversity in the Northern Gulf of Mexico. We assigned 73.7% of algal OTUs to genus and 59.6% to species ranks. Our current study detected molecular signals for 35 algal/protist species with no previous reports in the Gulf of Mexico, thus providing an important, molecular‐validated, baseline of species richness for this region. We also make several bioinformatic recommendations for the efficient use of high‐throughput sequence data to assess biological communities.     

Structure and species composition of ectomycorrhizal fungal communities colonizing seedlings and adult trees of Pinus montezumae in Mexican neotropical forests

Mexico is a center of diversity for pines, but few studies have examined the ectomycorrhizal (ECM) fungal communities associated with pines in this country. We investigated the ECM communities associated with Pinus montezumae seedlings and mature trees in neotropical forests of central Mexico and compared their structure and species composition. Root tips were sampled on both planted seedlings and naturally occurring adult trees. A total of 42 ECM operational taxonomic units (OTUs) was found on P.?montezumae. Diversity and similarity indices showed that community structure was similar for both plant growth stages, but phylogenetic diversity and Chao-estimated richness were higher for seedlings. Species composition differed between communities. The dominant OTUs belonged to the families Atheliaceae, Cortinariaceae, and Sebacinaceae, although different taxa appeared to colonize seedlings and adults. Only 12 OTUs were shared between seedlings and adults, which suggests that ECM fungi which colonize seedlings are still not fully incorporated into mycelial networks and that ECM taxa colonizing young individuals of P.?montezumae are likely to come from fungal propagules. Intra-generic diversity could be an insurance mechanism to maintain forest productivity under stressed conditions. This is the first report describing the abundance of Atheliaceae in tree roots in neotropical ecosystems.     

Cuticle Micromorphology of Pinus krempfii Lecomte (Pinaceae) and Additional Species from Southeast Asia

Cuticle micromorphology of the unusual Vietnamese pine, Pinus krempfii Lecomte, and three additional endemic southeast Asian species of Pinus L. (Pinaceae) is characterized for the first time. Taxa studied include (1) P. krempfii, typically placed in its own subgenus Ducampopinus (Chevalier) Ferré ex Little & Critchfield; (2) the endemic Vietnamese species Pinus dalatensis Ferré and (3) the southeast Asian species Pinus kwantungensis Chun ex Tsiang, both of subgenus Strobus; and (4) the widespread Asian species Pinus kesiya Royle ex Gordon of subgenus Pinus. The current and previous studies demonstrate that the genus Pinus and its subgenera are delimited by unique combinations of cuticular characters, although some of these characters may occur individually in other conifers. Cuticular micromorphology supports taxonomic assignment of P. krempfii to subgenus Strobus rather than to its own subgenus, a result that is also indicated by other anatomical studies and recent molecular studies. Sectional affinities of P. krempfii are usually with Parrya, subsection Krempfianae. An alternative classification of P. krempfii with subsection Gerardianae can be supported by micromorphological characters including broad cuticular bridges between stomata, details of the intercellular flanges of the epidermal cells, and usually an amphistomatic stomatal distribution. Features of other Asian species studied are consistent with their taxonomic assignments. The study demonstrates the utility of cuticle micromorphology to taxonomic delimitation within the family Pinaceae.     

山西太岳山油松群落对采伐干扰的生态响应

森林群落受到采伐干扰后的生态响应程度一直是森林生态学领域关注的研究前沿。本文以太岳山的油松林为对象,选择受不同采伐干扰强度和恢复时间的4块样地,通过固定标准地群落的调查获得数据资料,选用丰富度指数、Simpson指数（λ）、Shannon-Wiener指数（H'）、均匀度指数（E1）和Jaccard、Sprenson两种相似性指数,研究油松林对不同采伐方式生态响应,探讨不同采伐干扰强度和恢复时间下油松林生物多样性变化和更新演替规律。研究结果表明：1）受采伐干扰的样地中阳性植物的种类明显增多,随着恢复时间的增长,植物处于生长逐步旺盛、物种逐步丰富的阶段,其种类组成表现出由简单到复杂、由喜阳植物垄断到耐阴种类不断增多、种类由少变多的动态特征。2）适度的择伐可以提高群落整体的多样性,但皆伐则降低了群落的综合物种多样性。3）受相同择伐强度干扰后,群落之间保持了最高的相似性,皆伐干扰使群落环境有了本质的变化,与天然林的物种相似性最低。4）受采伐干扰后形成的次生林内,恢复初期中更新幼苗幼树出现6个树种,主要以油松和辽东栎（Quercus liaodungensi）为主。天然林中的环境最有利于油松幼苗的生长,择伐后恢复初期18a间幼树数量最高,幼苗数量最低,皆伐后更新幼苗幼树数量最少,环境条件最不利于更新。     

Independent origins of allotriploidy in the fish genus Poeciliopsis

We examined mitochondrial DNA (mtDNA) sequences and allozymes to assess possible modes of origin, clonal diversity, and evolutionary age in a triploid all-female fish of the genus Poeciliopsis from the state of Sinaloa, Mexico. Analysis of multilocus allozymes revealed that the Rio Mocorito biotype (Poeciliopsis monacha-lucida-viriosa) is trihybrid, carrying haploid genomes from three sexually reproducing species, Poeciliopsis monacha, Poeciliopsis lucida, and Poeciliopsis viriosa. Composite allozyme and mtDNA genotypes identified four clones, all bearing closely related mitochondrial haplotypes originally derived from P. monacha. Apparently these trihybrids arose endemically by addition of a haploid genome from P. viriosa, a local sexual species, to an allodiploid biotype, P. monacha-lucida, also found in the Rio Mocorito. The present analysis clearly revealed that P. monacha-lucida-viriosa arose independently of the two allotriploid biotypes that live in a river to the north (Rio Fuerte). Although the origins of allotriploidy in Poeciliopsis are less constrained phylogenetically and geographically than previously thought, known triploid biotypes all had relatively recent origins, which supports the notion that most asexual lineages are evolutionarily short-lived.