Looking for senescence in unorthodox organisms: A demographic life history analysis of an epiphytic lichen

Background/Question/Methods

The physiological organization of lichen thalli is fundamentally different from that of plants or higher animals, the taxa that have received the most demographic  study, and especially study of senescence in the field. To look for evidence of senescence  in lichens, we conducted a six- year demographic study of 400  Vulpicida pinastri individuals. This is a typical epiphytic lichen that specialized in relatively short-lived Alnus shrub substrates. Our field work occurred in the Wrangell Mts. of Alaska. 

Results/Conclusions

We parameterized a series of size- and age-structured demographic models with our data, accounting for both temporal and spatial variation in vital rates. Although this is a relatively short -lived species, we find no evidence of demographic senescence, although we do find that the life history of the species appears well-matched to the expected longevity of the substrates it inhabits, suggesting adaptive explanations for this species patterns of growth and mortality.