Habitat or temporal isolation: Unraveling herbivore–parasitoid speciation patterns using double digest RADseq

Abstract

Ecological speciation is often observed in phytophagous insects and their parasitoids due to divergent selection caused by host‐associated or temporal differences. Most previous studies have utilized limited genetic markers or distantly related species to look for reproductive barriers of speciation. In our study, we focus on closely related species of Lygus bugs and two sister species of Peristenus parasitoid wasps. Using mitochondrial DNA COI and genomewide SNPs generated using ddRADseq, we tested for potential effects of host‐associated differentiation (HAD) or temporal isolation in this system. While three species of Lygus are clearly delineated with both COI and SNPs, no evidence of HAD or temporal differentiation was detected. Two Peristenus sister species were supported by both sets of markers and separated temporally, with P. mellipes emerging early in June and attacking the first generation of Lygus, while P. howardi emerging later in August and attacking the second generation of their hosts. This is one of the few studies to examine closely related hosts and parasitoids to examine drivers of diversification. Given the results of this study, the Lygus‐Peristenus system demonstrates temporal isolation as a potential barrier to reproductive isolation for parasitoids, which could indicate higher parasitoid diversity in regions of multivoltine hosts. This study also demonstrates that incorporating systematics improves studies of parasitoid speciation, particularly by obtaining accurate host records through rearing, carefully delimiting cryptic species and examining population‐level differences with genomic‐scale data among closely related taxa.

Species complex diversification by host plant use in an herbivorous insect: The source of Puerto Rican cactus mealybug pest and implications for biological control

“…In this context, our results pointed to host plant use as an important driver of cryptic divergence in an a priori presumed polyphagous insects. Cryptic divergence has been recurrently observed in the form of host‐associated species that, very likely, diverged as the result of adaptation to alternate host plants with little morphological divergence in several insect species (Bagley, Sousa, Niemiller, & Linnen, 2017; Driscoe et al., 2019; Forbes et al., 2017; Matsubayashi, Kahono, & Katakura, 2011; Zhang, Bass, Fernández, & Sharanowski, 2018).…”

From Pavement to Population Genomics: Characterizing a Long-Established Non-native Ant in North America Through Citizen Science and ddRADseq

“…These techniques have proven useful to understanding species' invasion histories (Dupuis et al, 2018;Leydet et al, 2018;Bors et al, 2019;Cohen and Privman, 2019) and as a non-destructive method for identification and monitoring (reviewed in Taylor and Gemmell, 2016). More generally, emergence of RAD-based techniques have led to wide adoption of these methods in ecological and evolutionary studies of insects (Bagley et al, 2017;Storer et al, 2017;Lower et al, 2018;Zhang et al, 2018;De Jesús-Bonilla et al, 2019), including ants (Moreau and Wray, 2017;Boyle et al, 2018;Avril et al, 2019;Smith et al, 2019), which rank among the most damaging and difficult to control invasive species (Rabitsch, 2011).…”

Evolution of apetaly in the cosmopolitan genus Stellaria

“…BEAST version 2.5.1 was then used to estimate phylogenetic relationships across Stellaria under Calibrated Yule speciation and relaxed molecular clock models with a lognormal distribution (Bouckaert et al, 2014). A GTR+G+I model of molecular sequence evolution was specified given RAD loci exhibit a mixture of conserved and variant sites (Rubin et al, 2012; Zhang et al, 2018; Frajman et al, 2019; Paetzold et al, 2019). Four independent MCMC runs spanning 50 million generations each (with sampling every 5000th generation) were used to explore tree space under the specified parameters.…”