Data for: Phenotypic senescence in a natural insect population

Senescence seems to be universal in living organisms and plays a major
role in life-history strategies. Phenotypic senescence, the decline of
body condition and/or performance with age, is a largely understudied
component of senescence in natural insect populations, although it would
be important to understand how and why insects age under natural
conditions. We aimed (i) to investigate how body mass and thorax width
change with age in a natural population of the univoltine Clouded Apollo
butterfly (Parnassius mnemosyne, Lepidoptera: Papilionidae) and (ii) to
assess the relationship of this change with sex and wing length. We
studied a population between 2014 and 2020 using mark-recapture during the
whole flight period each year. Repeated measurements of body mass and
thorax width and single measurements of wing length were performed on
marked individuals. We analysed body mass and thorax width change with age
(days since marking), wing length and the date of the first capture. Both
body mass and thorax width declined non-linearly with age. Individuals
appearing earlier in the flight period had significantly higher initial
body mass and thorax width and their body mass declined faster than later
ones. Initial body sizes of females were higher, but males’ body sizes
decreased slower. Initial thorax width showed higher annual variation than
body mass. To our best knowledge, this is the first study that revealed
phenotypic senescence in a natural butterfly population, using in vivo
measurements. We found sexual differences in the rate of phenotypic
senescence. Despite the annual variation of initial body sizes, the rate
of senescence did not vary considerably across the years.