7414 Oxycoccus Hill
- Hill, Brit. Herb.: 324 (1756).
Notes: The status of Oxycoccus as genus is disputed. Vander Kloet (2009) included it in Vaccinium as sect. Oxycoccos and discussed its position, i.e., as possibly compromising the "naturalness" of Vaccinium if kept apart. A thorough treatment of the Oxycoccus group is Vander Kloet (1983). We provisionally keep Oxycoccus apart.
The occurrence of two or more ploidy levels in this group has been known for a long time (Hagerup 1940; Camp 1944; Darrow et al. 1944). The main morphological differences between the two species accepted below - Oxycoccus palustris (octoploid and dodecaploid) and O. microcarpus (tetraploid) - are found in leaf shape (oblong vs. ovate-lanceolate), shoot and pedicel pubescens (distinct vs. absent or very sparse), number of flowers (several together vs. usually single), sepals (pubescent along the margins vs. glabrous), and filament pubescence (hairs only on the edges vs. on both edges and planes). In addition, there are quantitative differences in nearly every organ. See also Vander Kloet (1983). Oxycoccus palustris and O. microcarpus sometimes co-occur and are then normally sharply different. Intermediate chromosome numbers are known. Some gene exchange via the hexaploid level might occur but we have seen no convincing documentation of it. Vander Kloet (2009) commented on the variation but did not accept two species or races for North America. Nearly every European author who has treated these plants in the last 40-50 years, does. The species concept becomes problematic if one does not accept as species taxa that differ consistently in several assumedly unrelated characters, are at different ploidy levels and with little or no documented gene exchange where co-occurring (except for first-generation hybrids), have overlapping site requirements, and have strongly overlapping ranges.
Higher Taxa
- Ericaceae [74,family]