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Plant Focus

Quercus macdougallii
A rare oak endemic to the Sierra Juárez in Oaxaca

Revisiting Quercus ×ganderi in Carl Wolf’s Footsteps

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Dirk Giseburt

Published May 2021 in International Oaks No. 32: 97–112

Abstract

More than 75 years ago, Carl B. Wolf published The Gander Oak, a New Hybrid Oak from San Diego County, California (Wolf 1944). He described Quercus ×ganderi C.B. Wolf 1944 as a hybrid of Q. kelloggii Newb. and Q. agrifolia var. oxyadenia (Torr.) J.T. Howell. He provided a description of the entity, identified the type locality and designated the holotype, indicated locations of several other nearby specimens, and provided line-drawing comparisons of leaves and acorns of the parent taxa and the hybrid. He also described a successful program of growing seedlings of the Gander oak and provided illustrative line drawings of leaves.

A chance encounter with the same tree in January 2019, when it had recently dropped a crop of acorns, yielded an opportunity to revisit some of Wolf ’s investigation and descriptions. This paper reconfirms some elements of Wolf ’s description in words and photographs and reports on the results of a second program of seedling propagation (with another comparative set of line drawings). While the primary goal of the study, perhaps, was to have some amateur botanical fun, with a nostalgic nod to an earlier explorer of California’s hybrid oaks, we also consider whether and how variation in seed morphology, specifically seed width, and seedling leaf morphology may hint at the genetic identity of the pollen source.

The strongest correlation in this small sample between acorn width and seedling leaf characters is with lamina thickness measured at leaf apex, with narrower acorns producing plants with thinner leaves and broader acorns producing plants with the highest median thickness value. This correlation is counterintuitive – of the parent taxa of the Gander oak, Q. agrifolia var. oxyadenia has the narrower acorn and Q. kelloggii has the more stout. The correlation between narrow acorns and relative thinness of seedling leaf may suggest either that narrower acorns indicate higher likelihood that Q. kelloggii is the pollen donor and/or that narrower acorns generally predict less vigorous plants. Seedlings with emergent leaf characteristics most typical of Q. kelloggii also have relatively thin laminas at apex.

Keywords

Quercus kelloggii, Q. agrifolia var. oxyadenia, seed morphology, leaf thickness, Agrifoliae.

References

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