Register now for our second annual NRS Research Symposium on Thursday, May 21st from 1 - 4 pm at the Martin Johnson House at Scripps Institution of Oceanography. Join us for posters and scientific talks on research from the four UC San Diego Natural Reserves.

Plan to enjoy the latest research on topics ranging from parasitic flatworms to plant-butterfly dynamics to soil microbiomes. Check out all the abstracts and the schedule for the afternoon. 

The City Nature Challenge, a global collaborative effort to document biodiversity using the platform iNaturalist, was a huge success. Globally, more than 103,000 people explored their backyards, local parks, and nature reserves, looking to photograph and share observations of biodiversity. In San Diego County, nearly 1,300 people contributed to the effort, with 71 of those observers photographing species at our UC San Diego Natural Reserves. Our docent-led walks resulted in photographs of 499 species, with dozens of species added to our species list that were not previously part of the iNaturalist record. This database helps us to better manage and study our reserves both now and in the future. 

Thank you to our collaborators from San Diego Bird Alliance and the San Diego Natural History Museum as well as all the observers, walk leaders, and identifiers who made this event possible. 

UC undergraduates, apply now for the fall 2026 California Ecology and Conservation Field Course. Students spend seven weeks at several UC Nature reserves across California. Find all the course details and apply here.  

Find all our upcoming events here. 

Scripps Coastal Reserve: Mesa docent-led walks

1st Saturdays, 9 - 11 AM

Scripps Coastal Reserve: Mesa weeding

Fridays, 8 - 10 am

Wander the Wetlands at Kendall-Frost Marsh Reserve

2nd and 4th Saturdays

9 - 11 AM

Native ant Camponotus anthrax, photographed at Elliott Chaparral Reserve by Jess Mullins 

Summarized by Trey Stowe, Roy Little Fellow. 

Effects of Habitat Fragmentation on Native Ants

In this 2021 study, researchers from the University of California, San Diego and the University of Illinois, Urbana-Champaign studied how habitat fragmentation and invasive species affect native ant populations over time. They did this by resurveying 40 habitat fragments and one unfragmented habitat in Southern California (Elliott Chaparral Reserve) 21 years after the initial study occurred in 1998. These surveys used pitfall traps, which were glass jars filled with water and a low toxicity antifreeze, in order to measure the amount of ants across the 41 habitats. These ants were collected to determine the change in quantity of native ants as compared to non-native ants, the change in distribution of the ants, and if the native ants show signs of recovery. After analyzing the 42,002 total ants collected, the researchers found that not only have Argentine ants (one of the invasive species of ants) increased in average abundance across all 40 fragmented habitats but also that they are increasing in how far they invade each habitat. Twenty-one years ago, Argentine ants would be rare (100 meters past the reserve's edge) but now the Argentine ants are only reducing in quantity past the 200 meter mark. On top of this, the native ants in these fragmented habitats did not show any signs of recovery, as previously predicted in the 1998 study.

However, when looking at the Elliott Chaparral reserve, of the 9,705 ants collected, none of the ants were non-native species. While this does not mean there are zero non-native ants in the reserve, this lack of any being recorded is indicative of just how little there are, especially when compared to fragmented habitats. This result demonstrates the power of nature reserves, as non-fragmented habitats are not nearly as impacted by edge effects, which can drastically impact a habitat's ability to function along its borders. The resistance of a reserve like the Elliott Chaparral reserve is found in its area to perimeter ratio, in which it has a much greater amount of internal area compared to its perimeter than a fragmented habitat, which would have a lower amount of internal area compared to its perimeter. This means that a large nature reserve can better regulate its native functions and protect itself against invasions from non-native or even invasive species.

Find the full paper here: Achury, R., Holway, D. A., & Suarez, A. V. (2021). Pervasive and persistent effects of ant invasion and fragmentation on native ant assemblages. Ecology, 102(3), 1–14. https://www.jstor.org/stable/26998120

There are four observations this month to show off the great work of the community scientists who documented biodiversity at our reserves during the City Nature Challenge, a collaborative effort to document biodiversity across the world from April 24 - 27. 

Post your own photos of native plants or animals on iNaturalist while visiting a NRS reserve (perhaps at one of the events above) for a chance to have your photo featured here next month. Check out all the observations collected at UC San Diego Reserves on iNaturalist.