Carya Glabra - Genetics

Genetics

Carya glabra var. megacarpa (Sarg.) Sarg., coast pignut hickory, was once recognized as a distinct variety but is now considered to be a synonym of C. glabra (Mill.) Sweet. C. leiodermis Sarg., swamp hickory, has also been added as a synonym of C. glabra (11).

Carya glabra (Mill.) Sweet var. glabra distinguishes the (typical) pignut hickory from red hickory (C. glabra var. odorata (Marsh.) Little). The taxonomic position of red hickory is controversial. The binomial C. ovalis (Wangenh.) Sarg. was published in 1913 for a segregate of C. glabra. It was reduced to a synonym of C. glabra in Little's 1953 checklist but was elevated to a variety in the 1979 edition (11). The principal difference is in the husk of the fruit, opening late and only partly, or remaining closed in C. glabra but promptly splitting to the base in C. ovalis. However, many trees are intermediate in this trait, and the recorded ranges are almost the same. The leaves of C. ovalis have mostly seven leaflets; those of C. glabra have mostly five leaflets. The two can be distinguished with certainty only in November. Since the two ranges seem to overlap, the distributions have been mapped together as a Carya glabra-ovalis complex (11).

Carya ovalis has also been treated as an interspecific hybrid between C. glabra and C. ovata. C. ovalis was accepted as a polymorphic species especially variable in the size and shape of its nuts and possibly a hybrid. The relationships may be more complex after a long and reticulate phylogeny, according to detailed chemical analyses of hickory nut oils.

One hybrid, C. x demareei Palmer (C. glabra x cordiformis) was described in 1937 from northeastern Arkansas.