Patterns of habitat affinity and Austral/Holarctic parallelism in dictynoid spiders (Araneae:Entelegynae)

Abstract

The ability to survive in a terrestrial environment was a major evolutionary hurdle for animals that, once passed, allowed the diversification of most arthropod and vertebrate lineages. Return to a truly aquatic lifestyle has occurred only rarely among terrestrial lineages, and is generally associated with modifications of the respiratory system to conserve oxygen and allow extended periods of apnea. Among chelicerates, in particular spiders, where the circulatory system also serves as a hydrostatic skeleton, very few taxa have exploited aquatic environments, though these environments are abundant and range from freshwater ponds to the marine intertidal and relictual (salt) lakes. The traditional systematic positions of the taxa inhabiting these environments are controversial. Partitioned Bayesian analysis using a doublet model for stems in the nearly complete 18S rRNA gene (~1800 nt) and in the D2 and D3 regions of the 28S rRNA gene (~690 nt), and standard models for loops and full protein-coding histone H3 (349 nt) partitions (totalling 3133 bp when aligned) of dictynoid spiders and related lineages revealed that the only truly aquatic spider species, Argyroneta aquatica (Clerck, 1767) (Cybaeidae Banks, 1892), belongs in a clade containing other taxa with unusual habitat affinities related to an aquatic existence, including occupation of semi-aquatic (intertidal) areas (Desidae Pocock, 1985: Paratheuma spp.) and highly alkaline salt-crusts (Dictynidae O. Pickard-Cambridge, 1871: Saltonia incerta (Banks, 1898)). In a contrasting pattern, other spiders that also occupy intertidal zones, including some other members of the family Desidae (Desis spp., Badumna longinqua (L. Koch, 1867)), are an independently derived clade found primarily in the southern hemisphere. Use of the doublet model reduced some branch-support values in the single-gene trees for rRNA data, but resulted in a robust combined-data phylogeny from 18S rRNA, 28S rRNA, and histone H3. This combination of results – reduction in support in single-gene trees and gain in support in combined-data trees –is consistent with use of the doublet model reducing problematic signal from non-independent base pairs in individual data partitions, resulting in improved resolution in the combined-data analyses.

The velvet spiders: an atlas of the Eresidae (Arachnida, Araneae)

“…7B). Association of Eresidae with Nicodamidae and Orbiculariae was anticipated and corroborated by the molecular studies of Spagna and Gillespie (2008) and of Spagna et al (2010). Eresidae was divided into two major clades: Seothyra , Dresserus , and Gandanameno form a southern and eastern African clade.…”

Rounding up the usual suspects: a standard target‐gene approach for resolving the interfamilial phylogenetic relationships of ecribellate orb‐weaving spiders with a new family‐rank classification (Araneae, Araneoidea)

“…Nevertheless, the morphological evidence for placing nicodamids near or far from orb‐weavers is not robust. It is molecular evidence, albeit from the same genes but with a diverse array of taxon samples, that strongly associates Nicodamoidea with Araneoidea (Blackledge et al., ; Miller et al., ; Spagna et al., ; Dimitrov et al., , ; Agnarsson et al., ), although Nicodamoidea was contradicted by Agnarsson et al. ().…”

The spider tree of life: phylogeny of Araneae based on target‐gene analyses from an extensive taxon sampling

“…A growing number of multi‐family target gene phylogenetic analyses are incrementally covering parts of the spider tree of life. These studies have focused on Mesothelae (Xu et al., ), Mygalomorphae (Bond et al., ; and references therein), Palpimanoidea (Wood et al., ), many on orb‐weavers (Blackledge et al., ; Dimitrov et al., ; and references therein), symphytognathoids (Rix et al., ; Lopardo et al., ; Lopardo and Hormiga, ), entelegynes (J. Miller et al., ; Spagna et al., ), the Oval Calamistrum (OC) clade (Polotow et al., ), psechrids (Agnarsson et al., ; Bayer and Schönhofer, ), eresids (Miller et al., ), pholcids (Dimitrov et al., ) and sparassids (Moradmand et al., ). These analyses show significant agreement as well as important contradictions.…”