Convergent evolution of the army ant syndrome and congruence in big-data phylogenetics

Abstract

The evolution of the suite of morphological and behavioral adaptations underlying the ecological success of army ants has been the subject of considerable debate. This "army ant syndrome" has been argued to have arisen once or multiple times within the ant subfamily Dorylinae. To address this question I generated data from 2,166 loci and a comprehensive taxon sampling for a phylogenetic investigation. Most analyses show strong support for convergent evolution of the army ant syndrome in the Old and New World but certain relationships are sensitive to analytics. I examine the signal present in this data set and find that conflict is diminished when only loci less likely to violate common phylogenetic model assumptions are considered. I also provide a temporal and spatial context for doryline evolution with timecalibrated, biogeographic, and diversification rate shift analyses. This study underscores the need for cautious analysis of phylogenomic data and calls for more efficient algorithms employing better-fitting models of molecular evolution.Key words: Dorylinae, phylogenomics, k-means, partitioning Significance Recent interpretation of army ant evolution holds that army ant behavior and morphology originated only once within the subfamily Dorylinae. An inspection of phylogenetic signal in a large new data set shows that support for this hypothesis may be driven by bias present in the data. Convergent evolution of the army ant syndrome is consistently supported when sequences violating assumptions of a commonly used model of sequence evolution are excluded from the analysis. This hypothesis also fits with a simple scenario of doryline biogeography. These results highlight the importance of careful evaluation of signal and conflict within phylogenomic data sets, even when taxon sampling is comprehensive.

Global domination by crazy ants: phylogenomics reveals biogeographical history and invasive species relationships in the genus Nylanderia (Hymenoptera: Formicidae)

“…The most recent Hymenoptera probe sets can capture up to as many as 2590 UCE loci from each specimen (Branstetter et al ., ). The increased accessibility and versatility of UCEs – combined with open collaboration across the ant systematics community – has incited an upswing of studies cutting across multiple timescales between families of Hymenoptera (Blaimer et al ., ; Faircloth et al ., ; Branstetter et al ., , ), and within subfamilies and tribes of Formicidae (Branstetter et al ., ; Blaimer et al ., ; Borowiec, ). Studies resolving ant phylogeny within genera, species, and even at the population level are among the most recent phylogenomic successes with UCE data (Blaimer et al ., ; Ješovnik et al ., ; Pierce et al ., ; Prebus, ; Ward & Branstetter, ; Branstetter & Longino, ).…”

Understanding UCEs: A Comprehensive Primer on Using Ultraconserved Elements for Arthropod Phylogenomics

“…Recent research also suggests phylogenomic results can be strongly affected by a tiny proportion of highly biased loci or sites (Shen et al 2017). With that in mind, we strongly encourage performing sensitivity analyses to test the robustness of results when interpreting phylogenomic data (Borowiec 2019, Camacho et al 2019.…”

“…In general, large data volumes associated with UCEs makes most Bayesian analyses too computationally intensive to be practical. To overcome this limitation, many studies reduce data size by removing taxa or loci in order to reduce the analysis time (Blaimer et al 2018b, Borowiec 2019).…”

Colony expansions underlie the evolution of army ant mass raiding

“…To infer the evolutionary relationship between group raiding and mass raiding, we combined our data on O. biroi with published descriptions of doryline biology, and mapped relevant life history traits to a consensus phylogeny of the Dorylinae (Table S2) (Borowiec, 2019). Ancestral state reconstructions suggest that the ancestral dorylines lived in small colonies, were specialist predators of ants, and indeed conducted scout-initiated group raids (Figure 2; Figure S3 to S5; Table S3).…”

“…We used the phylogenetic consensus topology of the Dorylinae from (Borowiec, 2019). We searched the natural history literature on doryline ants to find information on character states for a number of characters: colony size, prey spectrum, and various features of foraging behavior (raid initiation, recruitment, number of ants in the raid, and trail bifurcation) that are characteristic of either group or mass raiding behavior (Tables S1 and S2).…”