I recently had the opportunity to travel to Hyderabad, India. Traveling always provides a new perspective; my trip it provided some perspective on how we may view native plants here in South Florida.
Some of my research is on the genetics of native plants, and some is on the genetics of crop plants. I was visiting ICRISAT, the International Crop Research Institute of the Semi-Arid Tropics. ICRISAT breeds improved pigeonpea, chickpea, peanuts, sorghum, and pearl millet, five important tropical crops. With my collaborators Drs Doug Cook and Varma Penmetsa of the University of California at Davis, we visited Dr. Rajeev Varshney and his excellent research group in ICRISAT’s Center for Excellence in Genomics to discuss a project examining the consequences of domestication in chickpea.
Most of the crops on which we rely are grown on vast acreages far beyond the area in which our ancestors originally domesticated the crop. Many plant species have a limited natural range. For example, corn (maize) was domesticated from a wild grass native to a small part of southern Mexico, and now is grown over much of the world. In the United States, the only crop widely grown in proximity to the native plants from which it was domesticated is sunflower. The rest of our crops were originally domesticated in meso-America, South America, Asia, the middle east, or other distant lands. In other regions of the world, some crops are regularly grown in fields with native relatives of the crop growing at the edge of the field.
In India, several important pulses, or legumes, are grown in close proximity to their wild relatives: pigeonpea and all of the crop legumes of the genus Vigna (Cowpea/black-eyed pea, mungbean, black gram). These crops can hybridize with their wild relatives, share mutualistic microbes that convert inert atmospheric nitrogen (N2) into the building blocks of protein or provide limiting phosphorus that is the backbone of DNA. These cops can also be infected with diseases and attacked by herbivores that normally reside on native hosts. Hybridization between crop and wild relative may be common, and can be an important source of genetic variation for the crops. Despite the importance of these ecological interactions between the native wild species and crops, we know rather little about them.
Many of the tropical crops that do well in India grow well in Miami, with some effort. Black-eyed peas have done particularly well in my garden, tolerating summer heat and humidlity, my relatively shallow pine rockland karst soil, and my inattention to their needs. Pigeonpea, mung bean, and black gram seeds are less widely grown, but can do equally well. What I do not know, and would like to find out, is how these exotic plants interact with components of our native soils, such as symbiotic microbes. Although legumes may bring some of their microbes on their seed coat, they are likely to depend on microbes already here in the soil, borrowing the partners of our native plants. When we decide we are done gardening, and convert our yards back to native landscapes, do microbes favored by our garden plants (crop or ornamental) affect the success of our native plants?
There are so many interesting questions to ask here!
South Florida is where North America meets the Caribbean and Latin America. This is as true culturally as it is botanically. We have many plant groups where there are members here from both North America and the Caribbean. But North American and Caribbean plants in South Florida should have different histories that will have unique effects on their populations here.
South Florida is new land in geological time. Our land has only been above sea level for ~100,000 years. All plants here are immigrants from elsewhere, ether farther north in Florida or the Caribbean. They may have changed in the process of getting here, and be distinct as consequence of that immigration process.
For plants coming from more temperate parts of Florida, they would have had the chance to migrate in a front from farther north. Their migration south could have been contiguous so that new populations could continue to receive immigrants from neighboring populations. Most plants could have arrived at approximately the same time, and with a full community of soil symbionts, pollinators, herbivores, diseases, and any other organism that may affect them. Population sizes during the process of colonizing south Florida might have been relative large for these plants. But as these plants arrived in South Florida, they would have experienced soil types quite different from those farther north and a nw and challenging climate. Adaptation to these new conditions might have been slow.
For plants coming from the Caribbean, the distances and seawater would limit the number of immigrating individuals. Most new species would arrive in small numbers, meaning that their initial populations would be small. In these populations, inbreeding would be common. Furthermore, there would be a high possibility that random events like hurricanes or fires could knock out the entire population in one event. Caribbean plants might have arrived without their pollinators or the soil microbes on which they depend, as well as without many of the herbivores or diseases that kept them in check elsewhere. These changes could be advantageous or disadvantageous. In general, we might expect that Caribbean plants would be in many ways better pre-adapted to the climate, to the soils, and in many cases would thrive because they have long occurred on on similar soils in similar climates elsewhere in the Caribbean.
Do these differences matter for the conservation of native plants in south Florida? With ongoing climate change here altering conditions, I believe it must. But there is much more to know.