Potential study species

The reproductive biology of Cactaceae is not well known – only approximately 2% of the 2000 or so species have been studied (Mandujano et al, 2010). Consequently, how they interact with neighbouring plants of different species for pollinators or what this means in a community context are both virtually unknown. In one of the few published experiments that explicitly tested these interactions, researchers focused on the highly invasive prickly-pear Opuntia stricta in coastal shrublands in Catalonia (Bartomeus 2008). Cacti in the Opuntia genus are primarily bee-pollinated; they have large, colourful bowl-shaped flowers and many species are rich in pollen and nectar (Mandujano et al, 2010), suggesting they are very attractive to pollinators. Plants that exhibit these characteristics can interact with other plants in two notable ways for pollinators – they may act as a magnet plant, increasing local abundances of shared pollinators and thus facilitating the pollination of their neighbours, or conversely, they may steal pollinators and reduce the fitness of their neighbours.

To determine the effects of the invasion on the native plant community, the researchers created plant-pollinator interaction networks for both invaded and uninvaded sites. They found that O. stricta acted as a super-generalist in its new range. It was visited by 31% of the insect taxa in the invaded sites and was outcompeting native plants for pollination services. Within the same study, they found that Carpobrotus, an invasive succulent, had the opposite interaction with the surrounding plant community; it facilitated the pollination of the native plants in the system. This highlights the species-specific and context-dependent aspects of these interactions. There are a few species of Opuntia common in the Mojave Desert, and I hope to discover if and how they are interacting with other plants, particularly shrubs and their annual understory.

Attribution Stan Shebs [GFDL (http://www.gnu.org/copyleft/fdl.html), CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons

Bartomeus, I., Vilà, M., & Santamaría, L. (2008). Contrasting effects of invasive plants in plant–pollinator networks. Oecologia, 155(4), 761-770.

del Carmen Mandujano, M., Carrillo-Angeles, I., Martínez-Peralta, C., & Golubov, J. (2010). Reproductive biology of Cactaceae. In Desert plants (pp. 197-230). Springer Berlin Heidelberg.

UTM to longitude latitude R-code

UTM-long.lat conversions

Option 1. Work with original dataframe that has locations as UTM

library(rgdal)

utms <- SpatialPoints(data[, c(“long”, “lat”)], proj4string=CRS(“+proj=utm +zone=10”)) #create UTM matrix

longlats <- spTransform(utms, CRS(“+proj=longlat”)) #transform

Option 2. Generate a new dataframe and use coordinates function instead (preserves other vectors in dataframe)

#convert UTM to long.lat

mapdata <- data

coordinates(mapdata) <- ~long+lat #similar to SpatialPoints

proj4string(mapdata) <- CRS(“+proj=utm +zone=10”) #assign projection and coordinate reference system

longlats <- spTransform(mapdata, CRS(“+proj=longlat”)) #transform

Waiting for the rain

Rainfall updates

The growing season of 2015-2016 has come and gone with disappointing results from the supposed El Niño year. The 2016-2017 season is approaching and a few had feared that it would just continue the current pattern of drought. I was especially fearful having battling drought four years in a row in my study of plant interactions. It would be nice to have a chance with at least “average” precipitation amounts. Half way through the rain season and this year looks promising. Areas of California have been seeing some pretty significant precipitation including some potential floods. While this is great news in terms of drought relief for coastal cities and the Sierra Nevada snow pack, I wonder what the consequences will be for the deserts? In particular, the Mojave always seems to be in the unluckiest of rain shadows, missing most of the precipitation that the rest of the state experiences. I took a snap shot of the rainfall and average temperatures since seeding at the end of October. Here are the results:

Interpretation

The right combination of rain, temperature, and timing are absolutely crucial in desert ecosystems in regards to how the plant composition will respond. In an older paper by Beatley (1974) is a description of how these three variables determine plant composition. From this and my own experience, the absolute minimum rain to see any annual vegetation on the ground is 2.5 cm. However, these plants usually die within a month if there is no subsequent rain. I have seen this occur in multiple years where Halloween rain is not followed by any other precipitation until mid-January. The result? Many dead plants, and a new representation for plant communities. The Mojave has seen enough rain to begin germination and this rain has all occurred within the last 3 weeks. This, plus continued cold temperatures, should encourage the persistence of annuals for at least another month. If at least one other major rain storm passes through in that time I would expect to see these plants make it to flowering. On the more westerly side of the state, my sites have been seeing fairly consistent rain. This is great news for my Panoche Hills site that likely has passed its precipitation threshold that guarantees emerged plants to flowering.

Fingers crossed as always!