Impact of environmental factors on spider silk properties.

Spider orb webs have evolved to stop flying prey, fast and slow alike. One of the main web elements dissipating impact energy is the radial fibers, or major ampullate silks, which possess a toughness surpassing most man-made materials. Orb webs are extended phenotypes, and as such their architectural elements, including major ampullate silks, have been selected to optimize prey capture under the respective environmental conditions. In this study, we investigated the correlation of three landscape scales and three microhabitat characteristics with intrinsic silk properties (elastic modulus, yield stress, tensile strength, extensibility, and toughness) to understand underlying ecological patterns. For this purpose, we collected and mechanically tested major ampullate silks from 50 spider species inhabiting large altitudinal and climatic gradients in Colombia. Using regression analysis and model selection, we investigated the environmental drivers of inter- and intra-specific patterns of major ampullate silk properties, taking into account phylogenetic relatedness based on newly sequenced mitochondrial genomes. We found that the total amount of energy absorbed, i.e., toughness and tensile strength, is higher for fibers from species inhabiting regions where heavy rainfall is common. Interestingly, we observe the same general trend between individuals of the same species, stressing the importance of this environmental driver. We also observe a phylogenetic conservation in the relation of environmental variables with silk tensile strength and yield stress. In conclusion, the increase in major ampullate silk tensile strength and toughness may reflect an adaptation to prevent frequent rain damage to orb webs and the associated energetic loss.

Ocrepeira klamt sp. n. (Araneae: Araneidae), a novel spider species from an Andean páramo in Colombia.

Herein we describe Ocrepeira klamt sp. n. (Araneae: Araneidae), a new orb-weaving spider species from a Colombian páramo, which was formerly inaccessible for scientific studies due to decades long armed conflicts. Both, phenotypic and molecular data are used to confirm genus affiliation, and the new species is placed into phylogenetic context with other araneid spiders. Morphological characteristics and ecological notes of Ocrepeira klamt sp. n. are reported together with the sequence of the barcoding region of cytochrome c oxidase subunit I (COI) to provide a comprehensive description of the spider, facilitating future identification beyond taxonomic experts. With this study we contribute to the taxonomic knowledge that is required to inventory the hyper diverse yet threatened ecosystem of the Colombian páramos.

Parsimony analysis of unaligned sequence data: some clarifications.

De Laet (2015) claimed that minimization of ad hoc hypotheses of homoplasy does not lead to a preference for trivial optimizations when analysing unaligned sequence data, as claimed by Wheeler (2012; see also Kluge and Grant, 2006). In addition, De Laet asserted that Kluge and Grant's (2006) parsimony rationale is internally inconsistent in terms of Baker's (2003) theoretical framework. We argue that De Laet used extraneous presuppositions to critique Wheeler's position and, as such, his criticism should be considered cautiously in terms of its scope. Finally, we demonstrate that considering Kluge and Grant's parsimony rationale as inconsistent rests on De Laet's misunderstanding of the ideographic character concept and the consequences of relating it to Baker's rationale.

Revision and phylogenetic analysis of the orb-weaving spider genus Glenognatha Simon, 1887 (Araneae, Tetragnathidae).

A taxonomic revision and phylogenetic analysis of the spider genus Glenognatha Simon, 1887 is presented. This analysis is based on a data set including 24 Glenognatha species plus eight outgroups representing three related tetragnathine genera and one metaine as the root. These taxa were scored for 78 morphological characters. Parsimony was used as the optimality criterion and a sensitivity analysis was performed using different character weighting concavities. Seven unambiguous synapomorphies support the monophyly of Glenognatha. Some internal clades within the genus are well-supported and its relationships are discussed. Glenognatha as recovered includes 27 species, four of them only known from males. A species identification key and distribution maps are provided for all. New morphological data are also presented for thirteen previously described species. Glenognatha has a broad distribution occupying the Neartic, Afrotropic, Indo-Malaya, Oceania and Paleartic regions, but is more diverse in the Neotropics. The following eleven new species are described: G. vivianae n. sp., G. caaguara n. sp., G. boraceia n. sp. and G. timbira n. sp. from southeast Brazil, G. caparu n. sp., G. januari n. sp. and G. camisea n. sp. from the Amazonian region, G. mendezi n. sp., G. florezi n. sp. and G. patriceae n. sp. from northern Andes and G. gouldi n. sp. from Southern United States and central Mexico. Females of G. minuta Banks, 1898, G. gaujoni Simon, 1895 and G. gloriae (Petrunkevitch, 1930) and males of G. globosa (Petrunkevitch, 1925) and G. hirsutissima (Berland, 1935) are described for the first time. Three new combinations are proposed in congruence with the phylogenetic results: G. argyrostilba (O. P.-Cambridge, 1876) n. comb., G. dentata (Zhu & Wen, 1978) n. comb. and G. tangi (Zhu, Song & Zhang, 2003) n. comb., all previously included in Dyschiriognatha Simon, 1893. The following taxa are newly synonymized: Dyschiriognatha montana Simon, 1897, Glenognatha mira Bryant, 1945 and Glenognatha maelfaiti Baert, 1987 with Glenognatha argyrostilba (Pickard-Cambridge, 1876) and Glenognatha centralis Chamberlin, 1925 with Glenognatha minuta Banks, 1898.

Female genital morphology in the secondarily haplogyne spider genus Glenognatha Simon, 1887 (Araneae, Tetragnathidae), with comments on its phylogenetic significance.

Female genital morphology of secondarily haplogyne spiders has been poorly studied, hampering the analysis of its possible phylogenetic significance. We conduct a comparative morphological study of 12 species of the secondarily haplogyne spider genus Glenognatha Simon, 1887 using scanning electron microscopy. Representatives of the closely related genera Pachygnatha Sundevall, 1823 and Dyschiriognatha Simon, 1893 were also examined. The female genitalia of Glenognatha, Dyschiriognatha, and Pachygnatha species examined are composed of a spiracle-shape gonopore, a membranous chamber, a pair of copulatory ducts (CD) leading to spermathecae and a large uterus externus (UE). The most significant variation among Glenognatha species, previously unregistered within Araneoidea, is related with the absence or presence of CD and spermathecae. In addition, several characters as the form and distribution of long stem gland ductules and compartmentalization of the UE may be important for phylogenetic inference at species and generic level. Our results corroborate the close relationship between Dyshiriognatha and Glenognatha. A table with potentially informative female genitalic characters for phylogenetic inference within Glenognatha is provided. Understanding the general structure of the female genitalia in secondarily haplogyne taxa is a crucial step in order to propose characters for phylogenetic inference and to understand its possible functional significance.