Data for: Latitudinal variation in seasonal cycle mediates population differences in barnacle reproduction phenology

The timing of life history events around reproduction and early
development is critical in population dynamics, and it can determine
recruitment success, species dispersal, and population connectivity. In
ectotherms, as well as in plants and fungi, phenology is mediated by the
nonlinear effects of temperature on physiology and development, meaning
that spatiotemporal variation in temperature can exert powerful controls
on the timing of local reproduction and recruitment. Here, we examine
reproduction phenology (fertilization of embryos, duration of embryonic
development during brooding, and larval release) of the intertidal acorn
barnacle Semibalanus balanoides in 2002-04 and in 2019-24 at up to 8 sites
along a steep temperature gradient in the northwest Atlantic Ocean. At
each site and year, we assessed how phenology varied with intertidal
temperature, estimated with a hybrid atmosphere-ocean data assimilation
model. Although within-site reproduction was delayed due to interannual
and decadal fall warming (3.7 days per 1°C), fertilization at all sites in
all years still occurred within a 1-month timeframe. In contrast,
latitudinal differences in intertidal temperature resulted in
substantially different brooding durations (up to 95 days difference) and,
by extension, larval release timing (e.g., Dec 18 vs Apr 4). Consequently,
lower latitude larvae tended to enter the water column at the start of
winter, while higher latitude larvae were not released until spring. These
different larval release times result in regional differences in
temperature-mediated larval development, potentially resulting in lower
latitude populations experiencing greater dispersal. Our study is one of
the first to evaluate these relationships through both space and time in
natural populations, and we show that both spatial gradients and
interannual variation in the seasonal temperature cycle can mediate
reproductive physiology and dispersal of temperate and polar species.