Geographic cline and climatic effects on cone characteristics of natural populations of Pinus densiflora throughout the Japanese archipelago

ABSTRACT

Major conifer species with a widespread geographic distribution are growing under diverse climatic conditions. For such species, populations in regions with low resource availability, where producing additional cones is costly, presumably have more individuals that produce larger, highly viable cones with a higher resource-use efficiency. Geographic variations in cone characteristics (cone and seed size, seed production and productivity per cone) were examined for 28 Pinus densiflora natural populations (628 trees) across the species’ distribution in Japan. The degree of phenotypic differentiation across populations (P_ST) varied among the ten characteristics investigated. The average P_ST value (0.139) was higher than the previously reported neutral genetic variation of the species (F_ST = 0.013). The more northeastern populations produced cones of larger size (in length, width and mass), had higher seed production (number of filled seeds, seed mass per cone) and had higher seed productivity (indicators for seed production per cone development cost). A generalized linear mixed model showed that geographic variation in cone size and seed productivity per cone of populations was correlated negatively with annual solar radiation and mean temperature. The larger cone size and higher seed productivity per cone observed in northeastern populations support the hypothesis of higher resource-use efficiency, and could result from a genetic or plastic response under lower temperature and less radiation.

KEYWORDS:

• Climatic variable
• cone size
• Pinus densiflora
• reproductive behavior
• seed productivity per cone

Acknowledgments

We thank T. Nagamitsu for valuable suggestions and helpful comments on the manuscript before submission; the editor and two anonymous reviewers for their valuable suggestions and helpful comments during review processes. We also thank Y. Kawai-Munehara for the development of the map of the distribution range of P. densiflora using ArcGIS software; M. Ubukata, T. Nomura, N. Miyamoto, K. Yano, K. Hiraoka, Y. Shinozaki and the other members of the Forest Tree Breeding Center for their continued advice and encouragement during this study; and a number of people (unnamed here) for their kind help in collecting cone samples from the studied populations. We express our special thanks to K. Tanaka and H. Hatakeyama for their assistance in the measurements of cone characteristics.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.