For more about the Essig Museum click here or to donate now click the image below. Thanks for your support!
For more about the Essig Museum click here or to donate now click the image below. Thanks for your support!
Anna Holden who recently wrote a guest post here on insects from the La Brea Tar Pits as paleoenvironmental indicators has a lot more stunning insect fossils that have turned up during her studies. She is looking for help to identify more of the specimens. You can check out images of some of the material and if you have expertise in a group offer some suggestions as to the identification. Visit the Flickr account that she has created of ~44,000k year old insects from a unique assemblage. Comment there or for non-Flickr members you can email Anna comments aholden[at]amnh.org.
These insect fossil fragments are in near pristine preservation due to a rapid entrapment event that compacted this material into a camel (Camelops hesternus) skull.
I’ll be speaking tomorrow in a chemical ecology session about the carabid-Q project, in part.
Here is a reduced size pdf of the slides for preview or review. Enjoy.
I have the pleasure of participating in a couple projects that have poster presentations at this week’s 4th International Symposium of Carabidology in Athens, Georgia. One is on the Phylogeny of Adephaga (draft preview poster here: 6genes2treeposter-draft-locked)
The other is from the Carabid-Q team, detailing our new project on carabid defensive chemicals (draft preview poster here: carabid-q_poster_carabidology2016_locked-public ) The project is looking for students!
Enjoy! I hope to see you at this meeting or at ICE in Orlando.
My recent trip to Bozeman, MT wasn’t entirely fun and games. Well, it was entirely fun (Thanks, Mike!), but not all games. One objective was to collection samples of the various forms of Pterostichus (Hypherpes) protractus, the species of Hypherpes with the largest known range in the subgenus. This species has a distribution that stretches from just a bit north of Jasper, Alberta, Canada south to the Zuni and Sangre de Cristo Mountains in New Mexico, and west to northeastern Sierra Nevada Mountains and southeastern British Columbia.
With such a big range and a good deal of morphological variation, is anyone surprised that there are seven synonyms and six of those are T.L. Casey names? The area around Yellowstone was the last locality I needed (two Casey names from there) in my due diligence to sample areas in or near the type localities for all named species and get DNA quality specimens and males from across the entire range.
Part of my effort involved working in the MSU collection to look for localities. There were plenty of P. protractus records and so it was very easy to pick sites for sampling.
In addition to P. protractus, I expected to see Pterostichus restrictus, based a record of nine specimen records published by Hatch (1933) (in Hatch’s paper as Pterostichus longulus (see Bousquet 2012)). This is a species that I found to be very common in New Mexico and Colorado. But I couldn’t find any specimens in the collection. Mike helped me search through the old card records and voilà, there were nine records all from around Bozeman.
But… they were all really P. protractus. Sorry Montana, no P. restrictus for you. I doubt that P. restrictus ranges north of southern Wyoming. Hatch didn’t identify any specimens as P. protractus, so I suspect he was either unaware of the species or had a different concept in mind.
-Bousquet Y (2012) Catalogue of Geadephaga (Coleoptera, Adephaga) of America, north of Mexico. ZooKeys 1722, 1–1722.
-Hatch MH (1933) Records of Coleoptera from Montana. The Canadian Entomologist 65: 5-15.
Establishing Paleoclimate as a Means to Understand Current Climate Change
Scientists from the American Museum of Natural History, La Brea Tar Pits and Museum, UC Berkeley, UC, Irvine, and the California Academy of Sciences (CAS) are joining forces in an effort to use information from fossil insects to help establish what the Ice Age climate was like in southern California. This project is intended to help us answer questions such as: “To what degree can we predict the possible future climate of California from analogous, prehistoric data?” and “How have the flora and fauna responded to climatic changes over time?”
In California, we are currently experiencing one of the worst prolonged droughts in our recorded history (National Climate Assessment). While anthropogenic climate change may be one force driving the current episode, paleoenvironmental records indicate that this drought is not unique in the history of the region.
Although climate change impacts in southern California are well documented, our records only go back a century and a half at most. Deeper paleoenvironmental patterns must be reconstructed using other evidence. The Rancho La Brea (RLB) Tar Pits in southern California offers a wealth of fossils that can shed light on how the local environment has changed through time and these reach much further back than human records.
Insects as Paleoclimate Indicators
Though there is an abundance of insect material in the RLB deposit, this potential source of data has seen little use. Thanks to recent advances in reliable radiocarbon dating of disarticulated, identifiable beetle fragments from RLB (Holden and Southon, 2016), we are now in a position to date radiocarbon time as far back as 50,000 years or more, and are also able to date sufficient numbers of insect fossils such that they can provide a significant density of data for this period.
These developments have now been combined with methods using carabid and tenebrionid beetles as climate indicators. We can use these beetles as their present-day life-cycles, climate restrictions, and geographic distributions of the selected species are relatively well documented, and unlike migrating and often wide-ranging, mammals and birds, they offer crucial information about very local environments. Beetle species known from the Quaternary and even Tertiary are still extant and can reasonably be assumed to have flourished under the same climatic conditions that they do today.
A number of species of carabids and some tenebrionids have been used as paleoclimate indicators over the past decades. In particular, these predatory and scavenging species, whose behavior is reasonably well-documented, are known to find food in a variety of habitats and are not tied to specific types of vegetation. They are able to migrate into suitably warm or cool, wetter or drier habits, independent of the flora, as necessary. Therefore, they are expected to typically respond to fluctuations faster than plants (Elias, 2010).
Give this, generalist predator and scavenging insects may serve as better local indicators of change—in contrast, there may be a lag of hundreds of years for evidence of temperature changes to appear in pollen records (Elias, 2010). We expect that the rapid changes in populations of insects such as carabids and tenebrionids can reflect climate change that takes place within a matter of decades. Already entomologists are tracking the distribution of present day carabids and tenebrionids to record how they respond to current climate change.
Advances in Radiocarbon Dating Circumvent the Lack of Biostratigraphy* at RLB
For our initial step, we established a protocol to remove the asphalt matrix and other fossil preparation contaminants from the insect cuticle. This protocol works so effectively that it is now considered the most accurate procedure for radiocarbon dating insect cuticle from any Late Pleistocene deposit.
This method is invaluable for material from the RLB which lacks biostratigraphy as a means of establishing dates by association. Asphalt flows are characteristically intermittent and discontinuous and the result is mixing of fossils from different ages into the same layer.
Selecting the Right Insects for Analysis
The next step was to identify disarticulated fragments of carabids and tenebrionids with well-documented, narrow climate restrictions. Species also must be abundant enough in the RLB for destructive sampling and have enough mass to survive the chemical baths and then still have sufficient material remaining for radiocarbon combustion.
Kip Will (UC, Berkeley) and Rolf Aalbu (CAS associate) identified and contributed critical information on the ecology of the selected carabid and tenebrionid species. Systematists such as Kip and Rolf are fundamental to the success of this project because of their expertise in California species. They spend an inordinate amount of time in the field—thus, their experience on the ground, observing the behavior and the environments where their focal taxa live, provides the necessary, first-hand, detailed habitat information.
Extracting Climate data
We then associated a suite of informative bioclimatic variables from weather station data at Worldclim.org with hundreds of georeferenced natural history records for each species from CalBug, an open-access repository of occurrence data for California arthropods with contributions from thousands of collectors and data entry personnel. Selecting suitable records from those available for each of the target species resulted in a high-resolution data set.
So far, we have radiocarbon dated approximately 200 carabids and will soon have dates for 55 tenebrionids. The insect-based results are similar to what was found by Heusser et al. (2015) but notably different in one regard- there is no evidence for an earlier mesic interval. What might explain the difference?
Can distant pollen data adequately capture conditions at or near RLB and nearby locales? If we look at current conditions, it suggests that this may not be the case. Lake Elsinore is approximately 70 miles away, significantly farther from the ocean, and sits at nearly 400 meters above sea level compared to only about 50 meters above sea level at RLB. Therefore, assuming the two sites were equally dissimilar in the past, these paleoclimatic differences can easily be accounted for by microclimate differences between Elsinore and RLB.
How are these results novel?
These results challenge the widely-accepted interpretation of the paleoenvironment at RLB during the Late Pleistocene as being a cool, mesic climate, similar to that of modern-day Monterey, California (which is 450km north of RLB), or having approximately twice the amount of rainfall as typically falls at RLB now.
The standard story is largely based on a remarkably small number of plant identifications that have problematically been associated with 26-29,000 year old bone collagen dates (Friscia et al., 2008; Coltrain et al., 2004) from one RLB deposit, “Pit 91.”
Surprisingly, the dated insects from Pit 91 show a broad range from late Pleistocene to Holocene in the same grids where they are associated with the much narrower bone collagen-based date range; a clear demonstration of the RBL’s lack of biostratigraphy. This emphasizes the need to date individual samples and be very cautious about relying on dates based solely on associated samples. Reliance on such associations has led to persistent, and apparently mistaken paleoenvironmental and taphonomic inferences.
Why do our samples of insects show such a wide spread of ages? Intermittent and shallow asphalt pooling, not deep enough to immobilize larger animals, may have entrapped smaller organisms such as insects just like a pitfall trap that was opened sporadically to sample active and abundant species.
Previous investigators have provided some evidence for the paleoenvironment of southern California during the late Quaternary, but we still lack important details. Using the insects of RLB as climate and taphonomic indicators we can more clearly evaluate RLB’s significance for understanding other events such as the timing and agency of the megafaunal extinctions.
Stay tuned for even more results and other studies which use RLB insect fossils to better understand changes in southern California flora and fauna over time.
Many thanks to the scientists, staff and volunteers who have collected and input CalBug data required for this study. We also thank the scientists and staff at the La Brea Tar Pits and Museum and the American Museum of Natural History.
Together with a group of undergraduate students, I am comparing the trapping efficiency of standard pitfall cups and ramp traps. Preliminary results suggest that the ramp traps perform quite well. They catch a similar diversity of insects and don’t trap as many non-target critters like lizards and salamanders. But, we are still sorting and identifying samples from the Hopland Bioblitz, where we ran the traps, so I don’t have the final word yet.
The basic trap components are shown in the image above. The ramps are made from 5x7in sheet-metal flashing (on left) that you can buy at a hardware store in packs of 10. It would be cheaper to cut your own, but then you have to cut a lot of sheet metal, which is a hassle. For me, the precut pieces are worth it. Each ramp (in middle) has the sides bent up about 3/8in and a small tab cut and bent (image below) so that it fits and is held in the notch in the box. The box (on right) is a standard, empty pipette tip box with a notch cut out of each side. The lid is a handy, snap-on rain shield.
The sheet metal is slippery and so to make it rough and easy for insects to climb up, the inner surface of the ramp is painted with a mixture of metal priming paint and clean playground sand.
Assembled, the trap looks like the images above. When set up the field propylene glycol is put in the box. When you place the trap, be sure to push the ends of the ramps down into the dirt or leaf litter so that insects will walk right up the ramp and not go under it.
Building the traps takes more work than just going to the store and buying cups, but in the field, there is no digging, which means they can be set up quickly and easily. In the paper based on our study, we will explore in detail the pros and cons of each trap style, but it seems clear that ramp traps have a place in our standard insect collecting kit.