Divergent dynamics of sexual and habitat isolation at the transition between stick insect populations and species

Speciation is often viewed as a continuum along which populations diverge until they become reproductively-isolated species. However, such divergence may be heterogeneous, proceeding in `fits and bursts', rather than being uniform and gradual. We show in Timema stick insects that one form of reproductive isolation indeed evolves non-uniformly across this continuum, whereas another does not. Specifically, we use thousands of host-preference and mating trials to study habitat and sexual isolation among 42 pairs of taxa spanning a range of genomic differentiation and divergence time. We find that the evolution of habitat isolation is uncoupled from genomic differentiation within species, but accumulates linearly with it between species. In contrast, sexual isolation accumulates linearly across the speciation continuum. The results show different evolutionary dynamics for different components of reproductive isolation, indicate sudden transitions between phases of speciation, and highlight ..., Host preference was assayed using previously published protocols. Each evening, individual stick insects were placed in a 500-milliliter plastic cup with ~15 cm cuttings of two different host-plant species. The cups were covered with mosquito mesh and left overnight. In the morning we scored which of the two plant species the stick insect was resting upon (trials where neither was chosen were excluded). These experiments tested field-caught individuals within a few days of collection. Habitat isolation was estimated as the degree of divergence between taxon pairs in host-plant feeding preference. This was estimated by assigning one of the two host species used in each assay as the `reference host' and then calculating the absolute value of: (proportion of trials in which taxon 1 of the pair picked the reference host) - (the proportion of trials in which taxon 2 of the pair picked the reference host). Note that the assignment of a reference host is totally arbitrary as the degree of dive..., , # Data from: Divergent dynamics of sexual and habitat isolation at the transition between stick insect populations and species

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This dataset comprises measures of habitat isolation and sexual isolation from experiments, aligned DNA sequences, divergence time estimates, and variant (SNP) data for multiple species of *Timema* stick insects.

## Description of the data and file structure

Ten files are included in this dataset. The format of each is described below:

TimemaNucDNA.nex = DNA sequence alignment. This is a nexus format alignment file for an anonymous nuclear gene, Tc_nuc235.

HostRIDat.csv = csv file with host (habitat) isolation data. This file contains the raw data used to compute habitat isolation, along with associated metadata on the taxon pair types, species and population IDs and hosts tested. The key data are in the columns labeled PctPick1 and PctPick2, these give the percentage of individuals choosing a given host plant species from each of the two test populati...