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La Brea Beetles Revisited

LA BREA BEETLES REVISITED – TUESDAY, JUNE 6, STEVE CLARK – Anna Holden is the lead author of a new paper that examines beetle fragments from the La Brea Tar Pits in California. Anna discusses with entomologist Dr. Art Evans and 88.9 WCVE producer Steve Clark about how beetle bits -- tens of thousands of years old -- can provide insights into the climatic conditions that once prevailed at the Los Angeles Basin.

SC: I’m Steve Clark with Dr. Art Evans, entomologist, and this is What’s Bugging You.

AE: Beetles can tell us a lot about today’s environment. Anna Holden, doctoral candidate at the American Museum of Natural History’s Richard Gilder Graduate School and research associate at the La Brea Tar Pits and Museum is the lead author of a new paper talking about how fossil beetles can give us insights into the ancient climate of the Los Angeles Basin. Why beetles, Anna?

AH: It’s not only “why beetles?” but “which beetles?” Insects can have very particular ecological constraints, and in this case, the types of beetles that I’m working with, ground beetles and darkling beetles, often have very tight climate constraints. So by monitoring how they have responded to climate in the past gives us a sense of what the temperature was like in the past.

AE: So how old were these fossil beetles that you were looking at?

AH: Well, originally we thought that at the La Brea Tar Pits everything was late-Pleistocene or late-Ice Age.

AE: Which is how many years approximately?

AH: Approximately 50,000 or 40,000 to maybe 13,000, but my collaborator, Dr. John Southon from UC-Irvine and I developed a radiocarbon dating protocol, specifically for insects, and that only came out about a year ago.

AE: Wow.

AH: And when we radiocarbon dated the insects, we found out that there is continuity. These insects have been in the Los Angeles Basin 50,000 years ago, which is the limits of radiocarbon dating, all the way to the present.

AE: How many species did you look at in this study?

AH: For this particular study, we selected seven different species, and again, insects can have wide ecological constraints. In other words, they can be found throughout the country, because they can tolerate a wide range of temperature or precipitation, levels of rain. But I was looking, for again, these ground beetles or darkling beetles that are only found in particular types of environments and have very tight climate constraints.

AE: So what did your analysis show?

AH: I was very surprised to find out that all of these seven species were indicating the climate has been relatively stable for at least 50,000 years.

AE: Really?

AH: And this is with the exception, of course, of the last glacial maximum, and that is what it sounds like. Approximately 24,000 years ago, glaciers were at their literal maximum. So we do have a gap in beetle data for that time period, but otherwise, these are beetles that are still found in the same areas today.

AE: Now you assembled quite a varied team to analyze these beetles.

AH: This was definitely a group of people that probably would have no other reason to work together, but sometimes it takes that creativity to, you know, make an idea work. So we have Carabid specialists, we have Tenebrionid specialists, we have two beetle specialists, a radiocarbon dating specialist, someone who is very good at computer programming to help us work with a computer script to extract climate data, a paleoclimatologist, and myself -- a very diverse group of people that do not typically collaborate, but that’s what it took for us to be able to resolve the problems and come up with creative solutions.

AE: We’ll be sure to put a link up to let people know more about this fascinating work that you’re doing. Thank you so much.

AH: Thank you and thank you for having me back on your show.

SC: Dr. Art Evans is the author of Beetles of Eastern North America. You’ll find photos, audio, and a link to Art’s Facebook page at ideastations.org/radio/bugs.

Read an abstract of Anna’s article in Quaternary Science Reviews.

Visit here for more information about Anna’s research.