Host shifts are considered a key generator of insect biodiversity. For insects, adaptation to new host plants often requires changes in larval/pupal development and behavioural preference towards new hosts. Neurochemicals play key roles in both development and behaviour, and therefore provide a potential source for such synchronization. Here, we correlated life history timing, brain development, and corresponding levels of 14 neurochemicals in Rhagoletis pomonella (Diptera: Tephritidae), a species undergoing ecological speciation through an ongoing host shift from hawthorn to apple fruit. These races exhibit differences in pupal diapause timing as well as adult behavioural preference with respect to their hosts. This difference in behavioural preference is coupled with differences in neurophysiological response to host volatiles. We found that apple race pupae exhibited adult brain morphogenesis three weeks faster after an identical simulated winter than the hawthorn race, which correlated with significantly lower titres of several neurochemicals. In some cases, particularly biogenic amines, differences in titres were reflected in the mature adult stage, when host preference is exhibited. In summary, life history timing, neurochemical titre, and brain development can be coupled in this speciating system, providing new hypotheses for the origins of new species through host shifts.

Uploaded as part of this dataset are raw files collected in pursuit of results figure 1, s2, part 3.1 (brain development and brain morphology of apple and hawthorn race through developmental stage 1-8), figure s1(respiration data), figure 2, part 3.2 (brain morphology analysis post winter collection),  figure 3, part 3.3 (quantification of neuromodulators through the developmental stages) and figure 4, part 3.4 (Correlation between day post winter and quantification of neuromodulators from adult brain differentiation stage 4) of our manuscript.

The data for figure 1, s2, part 3.1, brain morphology of apple and hawthorn race, confocal images are divided into each stage, seven folders. The ".oib" files, labelled with "host race-each stage-magnification used-number given to brain sample", for example,apple-stage1-10x-B1”.  They are the raw stacks of images obtained via confocal microscopy, consisting of one channel capturing the neuropil marker at the 647 wavelength. Magnification was 10x, and 20x objective. Files can by opened in FIJI (Fiji: an open-source platform for biological-image analysis. Nat. Methods 9, 676–82). These files are raw files, before all processing. To replicate the results shown in the manuscript in Figure 1 and Supplementary Figure S2, one should consult the methods and supplementary methods of the manuscript, or the uploaded ReadMe file.

The data for figure s2 consists of 21 .xlsx files of raw data of respiration. Each file is labelled as “date of experiment-host race-cohort day-cohort date-age of pupae res”. File 22 has compiled data after classifying pupae into diapausing or non-diapausing groups. There are also two .pdf files. File 1, code1 (r script) of respiration data-classification of diapausing and non-diapausing pupae. File 2, code 2(r script) of respiration mixed effect analysis. For details on processing and analysis, one should consult the methods and supplementary methods of the manuscript or the uploaded ReadMe file.

The data for figure 2, part 3.2 brain morphology analysis post winter collection consists of two .xslx files with raw data and fit data calculation. This folder also contains code used to explain the proportion of individuals transitioning from stage 3 to stage 4 of brain development between apple and hawthorn flies, as well as to estimate 95% CIs around the logistic estimates.

The data for figure 3, part 3.3. quantification of neuromodulators using mass spectrometry. The folder for figure 3-mass raw data and analysis contains two main folders and one pdf file of code used to analyse the dataset. The individual PDF file contains Code (r script) for linear mixed model effect for neurotansmitter.pdf. One can replicate this analysis using R (V4.0.2, R Core Team. R: A Language and Environment for Statistical Computing. 2017.).

Folder A-raw mass spec files contain 15 .xlsx files for each mass spec run. This folder has detail about each mass spec batch with retention time detail, area ratio for each sample, standard curve, and calculated amount for each standard and sample run on that particular date. The file has been labelled the date of run, batch number and with developmental stage details. Folder B-outlier calculation contains 3 .xlsx files for stages 1-8 with compiled data from all the batches of mass spec run. Each file has all the details about host race, developmental stage, neurochemicals, amount in ng, batch number and outlier calculation.

The data for figure 3.4, to compare how these precursor neurochemicals titres changed over time between the developing hawthorn and apple race pupae, we compared neurochemical titres of Stage 4 brains against the day they were sampled after winter. The folder for figure 4-datasheets of stage 4 contains two datasheets used for analysis in SPSS software. File 1 contains stage 4 data for day 0-day 70. It also indicated host race, chemicals their amount and file detail used for univariate analysis. File 2 contains similar details as file 1 except excluding early time point data from day0-day 20.

Uploaded with these files is a master README file (Read Me file_kharva et al_2022) that describes all the main experimental parts included in this publication: Figure 1-4 and figure s1. This file also includes all methods from the manuscript, pulled from both the main paper and the supplementary methods, which were used to collect and analyze the data, as well as a listing of each associated file name.