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Gene Flow and a Mexican Metacollection in IOS Webinar #2
As acorns were falling off the trees throughout the Northern Hemisphere, IOS members gathered virtually for Webinar #2 on November 15, 2023, which was co-hosted by the Global Conservation Consortium for Oak. Once again, two different topics were combined, making the Webinar a really enjoyable and engaging experience for the whole audience.
This webinar came with some important announcements from IOS President, Roderick Cameron: the next IOS conference will be held in Oaxaca, Mexico in October 2025 with Pre and Post-Conference Tours that would make a total of 17 days dedicated to oaks. For 2024, there are plans for two Open Oak Day events in the UK and France during June and Tours in the Northern Hemisphere fall in California, Taiwan, and North and South Carolina (see details of these events here).
The first presentation by Dr. Andrew Hipp of the Morton Arboretum, titled “Gene Flow in Oaks”, covered a fascinating story about the hybridization of oaks. Although well known for hybridizing, oaks are still what is called “good species’’ and entities that we can recognize across their range. Hybridization is an opportunity for oaks to share alleles, increase their genetic variation through introgression, and evolve and adapt to new environments, often moving slowly from hybrids to new species in the process. Some beautiful examples of these processes were cited for Q. gambelii (which is probably the result of the gene flow between Q. lobata and Q. macrocarpa), Q. engelmannii (gene flow between Californian Q. berberidifolia and Mexican Q. oblongifolia), and for how Q. petraea used Q. robur’s pioneer populations to break north using pollen dispersal and introgression. In the recent work by Dr. Hipp and his group, the genetic coherence between Q. alba, Q. montana, Q. muehlenbergii, Q. stellata, Q. macrocarpa, Q. bicolor, and Q. michauxii was tested. Even though they used invariant markers, there was still evidence confirming the introgression between North American white oaks making this group of species a true white oak syngameon.1 Still, they are all good species in their range despite the long history of interspecific gene flow. This is in contrast to Europe’s three distinct refugia from which oaks moved northward and later intermixed as the glaciers receded; in eastern North American the white oaks seemed to be together during the last glacial maximum.
Currently, Dr. Hipp is working within a large collaboration consisting of several institutions from the US and two from China on a complex project tackling adaptive introgression in white oaks of Eastern North America and China. The group will integrate experimental studies with the collection of data from natural populations to understand how gene flow in two focal species, Q. macrocarpa and Q. serrata, shapes the communities of organisms in forests and savannas.
In the second part of the webinar, we were introduced to an oak collection at the University of Puebla Botanic Garden in Mexico through an inspiring presentation by Dr. Maricela Rodriguez (GCCO Mexico and Central American Coordinator) and Allen Coombes, Curator of Scientific Collections at the Botanic Garden.
Some of the first initiatives on the collection were as early as 1992 when the idea for national collections in botanical gardens was born. The work on an oak collection started in a small botanical garden (Louise Wardle de Camacho Botanic Garden, Puebla). This first attempt was unsuccessful, mostly due to inadequate horticultural practices. However, the situation started improving in 2007, particularly when Allen Coombes was appointed Curator of the Herbarium (available online at herbanwmex.net) and the Living Collection, and through field trips undertaken for the publishing of three books aimed at increasing the floristic inventory of Puebla. The main collection is situated in a dry climate, sometimes without rain for five months. Recently, three new external sites were introduced for the growth of oaks—in much more humid Xicotepec and Teziutlan in the north as well as one in the south in the Acapulco Botanic Garden. The collection keeps expanding from year to year. First, we saw some photographs of European oaks that grow pretty well in Puebla. These are primarily Mediterranean oaks such as Q. ilex, Q. suber, Q. rotundifolia, and Q. cerris. On the other hand, Q. robur suffers in these conditions, but is still able to produce some flowers. From the U.S., Q. buckleyi and Q. shumardii also showed very good growth in Puebla. As for Mexican oaks, the collection now includes around 50% of the native oak species and 11 of 32 threatened species. Recently, new actions were launched in the Garden in collaboration with The Morton Arboretum. These are conservation projects aimed at field exploration not only in Puebla but in other states as well aiming at single endangered species such as Q. hirtifolia, Q. brandegeei, Q. delgadoana, Q. insignis, and Q. rubramenta. The work continues towards increasing the number of threatened species supported by a Steward Training Program for Mexico and Central America, which aims to include more botanic gardens in Mexico and build a network that will support a metacollection2 of oaks.
The Webinar was a success, with even more participants than in the previous Webinar and an engaged discussion on both topics. Webinar #3 will take place in February.
IOS members can find a link to the recording of the webinar here.
1 A group of taxa that frequently engage in natural hybridization and lack strong reproductive barriers that prevent interbreeding.
2 The combined holdings of a group of collections.
