Cladistic biogeography of the Mexican transition zone

Biogeographic relationships among nine montane areas of endemism across the transition zone between North and South America are analysed cladistically based on phylogenetic hypotheses of thirty‐three resident monophyletic taxa of insects, fish, reptiles, and plants. Areas of endemism include the Arizona mountains (AZ), Sonoran Desert (SD), Sierra Madre Occidental (OCC), southern Sierra Madre Occidental (SOC), Sierra Madre Oriental (ORI), Sierra Transvolcanica (TRAN), Sierra Madre del Sur (SUR), Chiapan‐Guatemalan Highlands (CGH), and Talamancan Cordillera (TC). Area relationships are summarized using Brooks Parsimony Analysis and Assumption 0, with the former resulting in more defensible biogeographic hypotheses. Areas of endemism are dividable into two monophyletic groups; a northern group including AZ, SD, OCC, and ORI, and a southern group consisting of TC, CGH, TRAN, SUR, and the isolated southern regions of the Sierra Madre Occidental (SOC). The northern set of areas are characterized by recent, probably Pleistocene, isolation and prevalent widespread species, whereas the southerly areas probably diverged after Pliocene closure of the Panamanian isthmus. The southern areas are redundantly represented on many of the taxon‐area cladograms by endemic species, indicative of much higher levels of endemism in the Sierra Transvolcanica and further south. Use of a general area cladogram in such a transition zone permits explicit exploration of biogeographic patterns and establishes a predictive framework for taxonomy and conservation prioritization.     

Island evolutionary biogeography: analysis of the weevils (Coleoptera: Curculionidae) of the Falkland Islands (Islas Malvinas)

Aim I analysed distributional and phylogenetic information on weevils (Coleoptera: Curculionidae) from the Falklands, and integrated it with molecular, palaeontological and geological information to infer a geobiotic scenario. Location Falkland Islands (Islas Malvinas). Methods The panbiogeographical analysis was based on data on 23 Falkland species and their related taxa from southern South America. For the cladistic biogeographical analysis I analysed six weevil taxa for which phylogenetic hypotheses are available (the generic groups Cylydrorhinus, Strangaliodes and Falklandius, and the genera Antarctobius, Germainiellus and Puranius). Results from this analysis were compared with previous regionalizations. Cenocrons (sets of taxa that share the same biogeographical history) were identified by considering temporal information provided by fossils and molecular clocks. Finally, a geobiotic scenario was proposed by integrating the available information. Results Six generalized tracks were detected: Maule–Valdivian forests, Magellanic forest, Magellanic moorland, Falkland Islands, Magellanic forest–Magellanic moorland, and Magellanic forest–Falkland Islands. A node was identified in the Magellanic forest, based on the overlap of two generalized tracks. A single general area cladogram was obtained, implying the following sequence: (Magellanic moorland (Maule–Valdivian forests (Magellanic forest, Falkland Islands))). The Falklands are classified here as a biogeographical province in the Austral realm, Andean region and Subantarctic subregion. Falkland weevils seem to belong to a single Subantarctic cenocron. The sequence of events deduced implies the following steps: development of the Subantarctic biota in southern South America, arrival of the Falkland crustal block from South Africa in the Early Cretaceous, geodispersal of the Subantarctic cenocron from southern South America to the Falklands during the Early Oligocene, vicariance of the Magellanic moorland, vicariance of the Maule–Valdivian forests, and final vicariance between the Magellanic forest and the Falkland Islands. Main conclusions The biotic components identified support the connection of the Falkland weevils with the Magellanic forest. Falkland weevils belong to a single cenocron, dated to at least the Early Oligocene, when geodispersal from southern South America may have occurred. An older African cenocron may have been replaced completely by the Subantarctic one when the proto‐Falklands made contact with the Patagonian continental shelf. A geobiotic scenario implying vicariance events related to sea‐level variations could explain the distributional patterns analysed herein.     

Divergence time uncertainty and historical biogeography reconstruction – an example from Urophylleae (Rubiaceae)

Aim When hypotheses of historical biogeography are evaluated, age estimates of individual nodes in a phylogeny often have a direct impact on what explanation is concluded to be most likely. Confidence intervals of estimated divergence times obtained in molecular dating analyses are usually very large, but the uncertainty is rarely incorporated in biogeographical analyses. The aim of this study is to use the group Urophylleae, which has a disjunct pantropical distribution, to explore how the uncertainty in estimated divergence times affects conclusions in biogeographical analysis. Two hypotheses are evaluated: (1) long‐distance dispersal from Africa to Asia and the Neotropics, and (2) a continuous distribution in the boreotropics, probably involving migration across the North Atlantic Land Bridge, followed by isolation in equatorial refugia. Location Tropical and subtropical Asia, tropical Africa, and central and southern tropical America. Methods This study uses parsimony and Bayesian phylogenetic analyses of chloroplast DNA and nuclear ribosomal DNA data from 56 ingroup species, beast molecular dating and a Bayesian approach to dispersal–vicariance analysis (Bayes‐DIVA) to reconstruct the ancestral area of the group, and the dispersal–extinction–cladogenesis method to test biogeographical hypotheses. Results When the two models of geographic range evolution were compared using the maximum likelihood (ML) tree with mean estimates of divergence times, boreotropical migration was indicated to be much more likely than long‐distance dispersal. Analyses of a large sample of dated phylogenies did, however, show that this result was not consistent. The age estimate of one specific node had a major impact on likelihood values and on which model performed best. The results show that boreotropical migration provides a slightly better explanation of the geographical distribution patterns of extant Urophylleae than long‐distance dispersal. Main conclusions This study shows that results from biogeographical analyses based on single phylogenetic trees, such as a ML or consensus tree, can be misleading, and that it may be very important to take the uncertainty in age estimates into account. Methods that account for the uncertainty in topology, branch lengths and estimated divergence times are not commonly used in biogeographical inference today but should definitely be preferred in order to avoid unwarranted conclusions.     

Do fleas (Insecta: Siphonaptera) parallel their mammal host diversification in the Mexican transition zone?

Aim The Mexican transition zone is a complex area where Neotropical and Nearctic biotic elements overlap. A previous study on mammal species has shown a great diversification in the area. We analyse the diversification of their flea species (Insecta: Siphonaptera), in order to determine if a diversification similar to their mammal host species has occurred. Location The area analysed corresponds to Mexico. Methods The panbiogeographical or track analysis was based on the comparison of the individual tracks of 112 species belonging to 48 genera and eight families of the order Siphonaptera. Generalized tracks were obtained based on the comparison of the individual tracks. Nodes were found in the areas where generalized tracks overlapped. Results Thirty‐four generalized tracks were obtained, distributed within the Mexican transition zone (20), the Nearctic region plus the Mexican transition zone (8), the Nearctic region (4) and the Neotropical region plus the Mexican transition zone (2). In the areas where they intersected, 26 nodes were identified: 23 in the Mexican transition zone and 3 in the Nearctic region. Main conclusions The nodes are concentrated in the Transmexican Volcanic Belt (14), Sierra Madre Oriental (5) and Sierra Madre del Sur (4) provinces of the Mexican transition zone. These results show a significant diversification of the flea taxa, in parallel with the diversification of their mammal hosts.     

Process and pattern in the biogeography of New Zealand – a global microcosm?

Aim  To describe New Zealand's historical terrestrial biogeography and place this history in a wider Southern Hemisphere context.
Location  New Zealand.
Methods  The analysis is based primarily on literature on the distributions and relationships of New Zealand's terrestrial flora and fauna.
Results  New Zealand is shown to have a biota that has broad relationships, primarily around the cool Southern Hemisphere, as well as with New Caledonia to the north. There are hints of ancient Gondwanan taxa, although the long-argued predominance of taxa derived by vicariant processes, driven by plate tectonics and the fragmentation of Gondwana, is no longer accepted as a principal explanation of the biota's origins and relationships.
Main conclusions  Most of the terrestrial New Zealand flora and fauna has clearly arrived in New Zealand much more recently than the postulated separation of New Zealand from Gondwana, dated at c. 80 Ma. There is a view that New Zealand may have disappeared completely beneath the sea in the early Cenozoic, and acceptance of this would mean derivation of the entire biota by transoceanic dispersal. However, there are elements in the biota that seem to have broad distributions that date back to Gondwanan times, and also some that are thought unlikely to have been able to disperse to New Zealand across ocean gaps, especially freshwater organisms. Very strong connections to the biota of Australia, rather than to South America, are inconsistent with the timing of New Zealand's ancient and early separation from Gondwana and seem likely to have resulted from dispersal.     

The ups and downs of Mexican economic growth: the biological standard of living and inequality, 1870–1950

The secular change in the biological standard of living of the Mexican population between 1870 and 1950 is examined based on evidence on the physical stature from military and passport records. While Mexico industrialized and experienced rapid economic growth during this period, there was only a modest overall improvement in the height, health and nutritional status of the Mexican population. The average Mexican born in the 1940s was not only slightly taller than its compatriot of the 1870s. There were, however, considerable social differences: the Mexican upper class was markedly taller than the working class and the gap increased prior to the revolution. Economic growth with systemic inequality largely accounts for such a pattern.     

Phylogenetics and biogeography of Nephrolepis – a tale of old settlers and young tramps

The phylogenetic relationships and biogeographical history of the tropical genus Nephrolepis, a popular ornamental fern, are investigated using plastid DNA data from three regions: rbcL, rps4 plus the rps4‐trnS intergenic spacer (IGS) and the trnG intron plus the trnG‐trnR IGS. Our taxon sampling includes all but one of the 19 species of the genus. We confirm the monophyly of Nephrolepis, resolve infrageneric relationships and propose monophyly of the widespread species Nephrolepis biserrata and Nephrolepis abrupta, awaiting a denser sampling of Nephrolepis cordifolia and Nephrolepis undulata. The controversial inclusion of Nephrolepis in Lomariopsidaceae is not clearly supported. With a view to identifying synapomorphies for the clades retrieved, we reconstruct the evolution in Nephrolepis of sorus position and indusium shape. Finally, based on an estimation of divergence times and reconstruction of ancestral distributions for the genus, we propose an origin of the crown group in the Eocene in the forests of the Laurasian tropical belt, from where two main lineages would have dispersed and become isolated, one in the Neotropics and the other in Asia–Australasia. From this clear biogeographical pattern, some species, probably of Asian–Australasian origin, show recent range expansions, now spanning the Palaeotropics or the pantropical zone. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 113–127.     

Design – an inappropriate concept in evolutionary theory*

The concept of accident in evolution refers to causes which are stochastic with respect to selective demands arising from the external environment and acting on the organism, while the concept of design refers to causes which meet the requirement of these selective demands. The condition ‘with respect to selective demands’ is generally forgotten so that evolutionary changes are described as being design modifications. Design is an invalid synonym for adaptation. Further it implies a designer and has been used by some authors since before Darwin to argue that design in organisms demonstrates the existence of a designer and hence a plan. Yet if evolution depends on two simultaneously acting causes, one of which is accidental, then the process of evolution and all attributes of organisms are accidental. The concept of design is inappropriate in biology and should be eliminated from all biological explanations.     

Signatures of selection in the three‐spined stickleback along a small‐scale brackish water – freshwater transition zone

Local adaptation is often obvious when gene flow is impeded, such as observed at large spatial scales and across strong ecological contrasts. However, it becomes less certain at small scales such as between adjacent populations or across weak ecological contrasts, when gene flow is strong. While studies on genomic adaptation tend to focus on the former, less is known about the genomic targets of natural selection in the latter situation. In this study, we investigate genomic adaptation in populations of the three‐spined stickleback Gasterosteus aculeatus L. across a small‐scale ecological transition with salinities ranging from brackish to fresh. Adaptation to salinity has been repeatedly demonstrated in this species. A genome scan based on 87 microsatellite markers revealed only few signatures of selection, likely owing to the constraints that homogenizing gene flow puts on adaptive divergence. However, the detected loci appear repeatedly as targets of selection in similar studies of genomic adaptation in the three‐spined stickleback. We conclude that the signature of genomic selection in the face of strong gene flow is weak, yet detectable. We argue that the range of studies of genomic divergence should be extended to include more systems characterized by limited geographical and ecological isolation, which is often a realistic setting in nature.     

Karyotypic evolution and phylogeny of Mexican Passalidae (Coleoptera: Polyphaga: Scarabaeoidea)

The chromosomes of 26 taxa from Mexico of the tribes Passalini (three species) and Proculini (23 species) have been studied, increasing the karyotypically known species of the family Passalidae to 56. Karyotypic dynamism is high since the diploid number varies from 18 to 44 in the tribe Proculini. and from 25 to 31 in the tribe Passalini. In addition, supernumerary chromosomes, chromosome heteromorphism, translocations and possible sex multivalents have been found. These results contrast with the numerical conservatism found in related families of the superfamily Scarabaeoidea. However, both tribes are conservative with regard to sex determination, as all species of Proculini have male XY chromosomes whereas species of the Passalini have male XO chromosomes. It is postulated that differences in patterns shown by these two tribes are mainly due to population structure, because many species of Proculini are endemic to restricted areas of Meso and South America, favouring the settlement of karyotypic changes, whereas species of Passalini are distributed over large areas in the lowlands. It is also postulated that the ancestral karyotypic formula of the family is close to 12–14 pairs of autosomes although the ancestral male sex determination may be either XY or XO. At present only a weak relationship between morphological and karyotypic evolution has been found, which together with the marked numerical variability found within and between genera make it difficult to obtain phylogenetic conclusions from karyotypic results.     

Tibor Jermy (1917–2014)

Throughout the course of their evolution, plants have acquired a wide range of chemical and mechanical defenses to protect against herbivores. Ehrlich & Raven's coevolutionary theory suggests that this diversification of defensive traits is driven by the strong impact of novel traits on insect herbivores. However, the impact of plant defenses on insects is difficult to compare between related plant species due to variation in environmental and biotic conditions. We standardized these factors as far as possible by analyzing the effects of chemical and mechanical defensive traits on insects in a local community of 11 Salicaceae species growing in sympatry, and their leaf‐chewing herbivores. Defensive traits (salicylates, flavonoids, tannins, trichomes, and leaf toughness) were generally not inter‐correlated, with the exception of a negative correlation between salicylates and trichomes. The content of salicylates, a novel group of defensive metabolites in the Salicaceae, was correlated with low herbivore diversity and high host specificity. Despite these effects, the phylogeny of the studied species shows loss of salicylates in some Salix species instead of their further diversification. This could be due to salicylates not decreasing the overall abundance of herbivores, despite accounting for up to 22% of the dry leaf mass and therefore being costly. The defense of low‐salicylate willow species is thus probably maintained by other defensive traits, such as trichomes. Our study shows that the balance between costs and benefits of defensive traits is not necessarily in favor of novel compounds and illustrates a process, which may lead to the reduction in a defensive trait.     

New Mexican species of Byttneria (Sterculiaceae), Bakeridesia (Malvaceae), and Triumfetta (Tiliaceae)

Recent collections have brought to light the following new species from the states of Tabasco and Oaxaca, Mexico:Byttneria fluvialis (Sterculiaceae) from Tabasco;Bakeridesia amoena (Malvaceae), andTriumfetta calzadae (Tiliaceae) from Oaxaca.     

The epidemiologic transition in a frontier town — Manti,Utah: 1849–1977

Census reports and information in burial records of Manti, Utah from 1849 to July 1977 are examined in order to (1)document mortality trends and differentials by age, sex, cause-of-death, and seasonality as Manti passed from a frontier settlement to a rural agricultural community; and (2) ascertain whether the shifts in the cause-of-death structure follow those patterns outlined by Omran (1971, 1974, 1977) in his theory of the epidemiologic transition. Findings parallel patterns suggested by Omran. Major factors accounting for mortality reductions are (1) elimination of the population's dependence upon a contaminated water supply, and (2) adoption of medical advances as they became available.     

Molecular phylogeny and systematics of the Pieridae (Lepidoptera: Papilionoidea): higher classification and biogeography

The systematic relationships of the butterfly family Pieridae are poorly understood. Much of our current understanding is based primarily on detailed morphological observations made 50–70 years ago. However, the family and its putative four subfamilies and two tribes, have rarely been subjected to rigorous phylogenetic analysis. Here we present results based on an analysis of molecular characters used to reconstruct the phylogeny of the Pieridae in order to infer higher‐level classification above the generic level and patterns of historical biogeography. Our sample contained 90 taxa representing 74 genera and six subgenera, or 89% of all genera recognized in the family. Three complementary approaches were employed: (1) a combined analysis of a 30 taxon subset for sequences from four gene regions, including elongation factor‐1 alpha (EF‐1α), wingless, cytochrome oxidase subunit I (COI), and 28S (3675 bp, 1031 parsimony‐informative characters), mainly to establish higher‐level relationships, (2) a single‐gene analysis of the 90 taxon data set for sequences from EF‐1α (1066 bp, 364 parsimony‐informative characters), mainly to establish lower‐level relationships, and (3) an all available data analysis of the entire data set for sequences from the four genes, to recover both deep and shallow nodes. Analyses using maximum parsimony, maximum likelihood and Bayesian inference provided similar results. All supported monophyly for the four subfamilies but not for the two tribes, with the Anthocharidini polyphyletic and the Pierini paraphyletic. The combined and all available data analyses support the following relationships among the subfamilies: ((Pseudopontiinae + Dismorphiinae) + (Coliadinae + Pierinae)), corroborating Ehrlich’s 1958 phenetic hypothesis. On the basis of these analyses, and additional morphological and life history evidence, we propose a reclassification of the subfamily Pierinae into two tribes (Anthocharidini s.s., Pierini s.s.) and two informal groups (Colotis group, Leptosia), with the tribe Pierini s.s. subdivided into three subtribes (Appiadina, Pierina, Aporiina) and three genera (Elodina, Dixeia, Belenois) of uncertain status (incertae sedis). The combined and all available data analyses support the following relationships among the Pierinae: (Colotis group + Anthocharidini s.s. + Leptosia + (Elodina + ((Dixeia + Belenois) + Appiadina + Pierina + Aporiina))). Application of a molecular clock calibrated using fossil evidence and semiparametric rate smoothing suggests that divergence between the Pierina and Aporiina occurred no later than the Palaeocene (> 60 Myr). The minimum estimate for the age of the crown‐group of the Pieridae was 112–82 Myr, with a mean of 95 Myr. A historical biogeographical hypothesis is proposed to explain the present‐day distribution of the clade Pseudopontiinae + Dismorphiinae, which argues for an origin of the two subfamilies in western Gondwana (Africa + South America) during the Late Cretaceous. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society, 2006, 147 , 239–275.