Surf and turf: A dataset of stable isotope values of plants and animals from southern California

This article presents baseline isotope values for plant and animal samples collected from across southern California. A total of 80 samples representing 50 species were collected and analyzed for this project. This original dataset includes 31 plant species, 13 finfish species, 3 mollusk species, 2 crustacean species, and 1 echinoderm. Plant samples were collected by the authors and an undergraduate research assistant in San Diego and Santa Barbara counties. Animal samples were procured from local fishers in San Diego and Santa Barbara. All samples were subjected to stable isotope analysis at the University of California, San Diego (UCSD). In this paper we present our new δ13C and δ15N data alongside previously published values from three other studies [1], [2], [3]. The previously published values reproduced here were derived from a mix of modern and archaeological samples. Together, these data represent the most complete dataset currently available for southern California baseline stable isotope values. The full combined dataset can be found in the Supplemental Data included with this paper, while Table 1 presents a comparison of defatted and untreated faunal specimens. These data will be of use to archaeologists and ecologists conducting future isotope studies on the Pacific Coast of North America.

Archaeology Specific subject area Historical ecology and paleodiets in southern California. Type of data Table  How data were acquired Plant and animal samples were collected in San Diego and Santa Barbara counties of southern California and processed at the UCSD Paleodiet Laboratory, directed by Dr. Margaret Schoeninger. Plant samples were cleaned, shredded, dried, then reduced to a fine powder using an agate mortar and pestle and a fine sieve (U.S. 100, 149 microns). Finfish and invertebrate soft tissue samples were removed from the organism with a stainless-steel scalpel and cut into small pieces ( ∼2, 3 mm diam.

Value of the Data
• These data present the most complete set of δ 13 C and δ 15 N values currently available for plant and animal food sources that may have been used by ancient populations in southern California. • These data will be of interest to Archaeologists and Historical Ecologists working in southern California or the Pacific Coast of North America. • Future studies of paleodiets in southern California or Pacific North America will be able to use the values presented here as a baseline to interpret human isotope data. • Dataset presented here greatly expands coverage of marine and maritime foods compared to previous baseline stable isotope studies. • Studies of historical ecology or human paleodiets focusing on marine and coastal environments around the world will be able use these values as a point of comparison.

Data Description
Supplemental Data . This table presents a combined set of available baseline stable isotope  data for possible human foods in southern California. This table includes values from 80 samples processed by the authors for this study, as well as 79 values taken from previous studies.  Together these data represent the largest currently available baseline stable isotope library for  southern California.  Table 1 . This table presents a comparison of stable isotope values for defatted and untreated faunal specimens processed for this study (see experimental design).

Experimental Design, Materials and Methods
The goal of this project was to compile a baseline database of δ 13 C and δ 15 N values of plant and animal species that may have been consumed by ancient human populations across southern California in order to further our ability to reconstruct dietary patterns and environmental changes over time. Previous baseline isotope studies from the region mainly targeted marine and terrestrial mammals and terrestrial plants [1][2][3] , making the expansion of coverage of marine food resources a major focus for this study. We analyzed 80 samples collected from across southern California for this project (see Supplemental Data). A total of 50 different species are represented in the dataset, including 31 plant species, 13 finfish species, 3 mollusk species, 2 crustacean species, and 1 echinoderm. When collecting samples for this study we primarily targeted foods that were mentioned as being consumed by indigenous populations in the ethnohistoric record for the region [5] . The collection of all samples took place between 2014 and 2017 and was carried out by the authors of this paper as well as an undergraduate research assistant.
We collected and analyzed 40 plant samples representing 31 different species for this project. Samples were collected from locations across both San Diego and Santa Barbara counties in southern California. Areas targeted included northern San Diego County, as well as the Mission Canyon area of Santa Barbara and trails along the Camino Cielo north of Santa Barbara. Samples were often collected during hikes by the authors or the undergraduate assistant in the aforementioned areas. All plant sample collection occurred during 2015 and 2016 and took place throughout the year. Our Western Sea Purslane ( Sesuvium verrucosum ) sample, was grown from seed at the Biology Field Station at UCSD. The experimental garden at the University of California, San Diego (UCSD) Biology Field Station using local soils and captured rainwater in order to reproduce a natural environment.
When selecting plant samples for analysis we attempted to target plants that are documented as having been used by indigenous groups in southern California. Out of the 31 plant species found in our database, 26 were consumed as food or as medicine by indigenous southern Californian groups [5] . This includes major food resources such as red maids ( Calandrinia ciliate ), blue dicks ( Dichelostemma capitatum ), toyon berry ( Heteromeles arbitifolia ), holly-leaved cherry seeds ( Prunus ilicifolia ), and acorns ( Quercus sp.). Other plants included in this study were consumed as tea for medicinal purposes. Plants consumed as teas for medicinal purposes include yerba mansa ( Anemopsis californica ) California croton ( Croton californicus ), longstem buckwheat (Erigonum elongatum). California wild rose ( Rosa californica ), and white sage ( Salvia alpina ). Milkweed ( Asclepias sp.) was not consumed intentionally but was used as a chewing gum. Four species ( Epilobium canum, Keckiella cordifolia, Matteuccia struthiopteris, and Sequoia sempervirens ) were not consumed but were instead used for construction or for topical medical purposes but are nonetheless included in our database.
In addition to plant resources, we analyzed a total of 40 marine animal samples representing 19 different species. All finfish samples were taken from wild specimens caught in the Pacific Ocean off the shore of southern California during June of 2016. Most of these samples were purchased from local fishers at the Dockside Harbor Market in San Diego or at Saturday morning Santa Barbara Harbor fish market. These samples were purchased for this project and would have otherwise been sold commercially. One sardine ( Sardinops sagax ) was donated to the authors by local recreational fisher. Crustacean and echinoderm samples were also purchased from local fishers at the Santa Barbara harbor market. Mussel samples ( Mytilus californianus ) were collected in Santa Barbara County by the authors, while the turban snail ( Megastraea undosa ) sample was also purchased at the Santa Barbara Harbor market. Because no animal subjects were alive when acquired for research, no care or use of live animals were preformed and the research is thus not subject to the National Institutes of Health guide for the care and use of Laboratory animals (NIH Publications No. 8023, revised 1978). Processing of field samples for stable isotope analysis was conducted at the Paleodiet Laboratory at the University of California, San Diego. Laboratory work was conducted by the authors as well as by undergraduate research assistants. Plant samples were placed in glass beakers with ∼80 mL of double distilled water and cleaned in an ultrasonic bath for 15 min. Plant samples were then shredded in a blender (MagicBullet by NutriBullet), dried between 24 and 48 h at 60 °C in a laboratory oven, and then reduced to powder by grinding in an agate mortar and pestle. Powdered plant samples were then passed through a fine sieve (U.S. 100, 149 microns) to homogenize particle sizes. Samples of finfish and invertebrate flesh were removed from the organism with a stainless steel scalpel and cut into small pieces ( ∼2, 3 mm diam.). Flesh samples were then divided into two aliquots. Because lipids are more depleted in 13 C than other tissues [6] , one aliquot was subjected to a lipid extraction procedure and the other was left untreated. The first aliquot received a 2:1 chloroform: methanol (v/v) treatment for 20 min in an ultrasonic bath to remove lipids, followed by a 10 min ultrasonic bath in double distilled water to remove any remaining adhering lipids. The second aliquot received no treatment. Both aliquots were subsequently frozen and then lyophilized using a Labconco benchtop (50 L) freeze dryer set at -50 °C and 0.133 mb for 24 h.
Stable isotope analyses were conducted in the Analytical Facility at the Scripps Institution of Oceanography Measured δ 13 C and δ 15 N values for each of our samples are reported in the Supplemental Data included with this paper. Also included in the Supplemental Data are corrected δ 13 C values to account for the Suess effect as well as for differences between biological tissue types.
The Suess effect refers to modern depletion of δ 13 C values in atmospheric CO 2 caused by the burning of fossil fuels. All modern plant and animal δ 13 C values were corrected to the preindustrial mean using compiled historical records of atmostpheric δ 13 C values [7] . This correction varied between modern samples collected for the present study and hare samples collected in the 1960s and early 1970s. Differential impacts of the Suess effect on δ 13 C values in marine versus terrestrial environments are accounted for by multiplying the Suess effect correction by 0.65 [ 8 , 9 ]. As δ 13 C collagen values are approximately 1.0 ‰ higher than δ 13 C muscle values [ 10 , 11 ] we subtracted this amount from terrestrial mammal and otter bone collagen values. For cetaceans and pinnipeds, however, we assumed that a major portion of consumed tissues would have been comprised of blubber, which is depleted in 13 C relative to flesh. For these species we therefore subtracted 5.6 ‰ from bone collagen δ 13 C values following previous work by Newsome et al. [10] . We assumed muscle and bone collagen δ 15 N values to be equivalent [9] .
In addition to the plant and animal samples analyzed as part of this study, we supplement our baseline isotope database with additional data from previously analyzed plant, terrestrial mammals, marine mammals, and invertebrate samples (Supplemental Data). This included the stable isotope values from 36 modern terrestrial plants [1] , and nine terrestrial mammals, including two modern hares ( Lepus spp.) [3] and seven archaeological deer ( Odocoileus hemionus ) [1] . Supplemental marine specimens include seven invertebrates [2] , and 24 archaeological marine mammals [1] . A comparison of stable isotope values, the percent C and N values, and the C:N ratios for defatted and untreated faunal specimens can be found in Table 1 . Together these data represent the largest currently available baseline stable isotope dataset for southern California. Interpretations from the application of this new baseline database to human isotope datasets using Bayesian mixing models can be found in the research article co-submitted with this data paper [4] .

Ethics Statement
This work did not involve the use of human subjects or data collected from social media platforms. The project did not involve any in vivo or live animal experiments and was therefore carried out in accordance with the National Institutes of Health guide for the care and use of Laboratory animals (NIH Publications No. 8023, revised 1978) as well as the ARRIVE guidelines for reporting of in vivo experiments.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships which have or could be perceived to have influenced the work reported in this article.