Growth and secondary compound investments in the epiphytic lichens Lobaria pulmonaria and Hypogymnia occidentalis transplanted along an altitudinal gradient in British Columbia

Abstract

We investigated altitudinal variation (550–1650 m) in relative growth rates (RGR) and carbon-based secondary compounds (CBSC) in the cephalolichen Lobaria pulmonaria (L.) Hoffm. and the chlorolichen Hypogymnia occidentalis L. H. Pike transplanted for 14 months in a U-shaped valley in inland southern British Columbia. Prior to transplantation, half of the thalli were treated with phosphorus (P) to examine effects of P on carbon allocation. Growth in L. pulmonaria was substantially higher in the toe-slope position, corresponding to much higher bark pH. Sixty-four percent of the variation in RGR was accounted for by positive pH effects and adverse effects of direct light exposure in the best subset multiple regression model. For H. occidentalis, 57% of the variation in RGR was accounted for by positive and negative effects of indirect and direct light, respectively. Neither altitude nor P had a noticeable effect on RGR, the former possibly reflecting a trade-off between orographic precipitation and inversion-boosted nocturnal dew in valley bottom localities. Neither was there any correlation between altitude and CBSCs, although treatment with P did significantly trigger secondary metabolism in L. pulmonaria, but not in H. occidentalis. No significant intraspecific relationship between growth and CBSC investments was noted.