Botany
Endemism in native California Channel Island floras correlated with seasonal patterns of aeolian processes.
Journal: Botany
Manuscript ID cjb-2015-0143.R1
Manuscript Type: Note
Date Submitted by the Author: 02-Nov-2015
Complete List of Authors: Riley, Lynn; University of South Dakota, Biology McGlaughlin, Mitchell; University of Northern Colorado, Biological Sciences
Keyword: aeolian, CaliforniaDraft Channel Islands, dispersal, endemism, plant diversity
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Endemism in native California Channel Island floras correlated with seasonal patterns of
aeolian processes.
Lynn Riley 1 and Mitchell E. McGlaughlin 2
1 – Department of Biology, University of South Dakota, Vermillion, SD 57069;
2 – School of Biological Sciences, University of Northern Colorado, Greeley, CO, 80639;
[email protected] Draft Corresponding Author: Lynn Riley, Department of Biology, University of South Dakota,
414 East Clark St., Vermillion, SD 57069, [email protected], Fax: 605-677-6557
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ABSTRACT
This study revisits the hypothesis that dispersal to the California Channel Islands follows a stepping-stone pattern from mainland California, based on earlier work indicating the floras conform to classic island-biogeographic expectations. A re-examination of data incorporating directions of prevailing and seasonal Santa Ana winds greatly strengthens the power of the model to explain levels of endemism in Channel Island floras and suggests the importance of aoelian processes for island colonization. Regression analysis of percent endemism in the native flora against distances measured along the axis of winds improves the r2 from 0.099 to 0.482. The endemic species that flower in the dry season as a percent of the native flora of the islands is also strongly related to these revised source distances ( r2 = 0.665).Draft Furthermore, the native floras of the southern islands are nested subsets of the floras of the northern islands, and angiosperm flowering peaks during the dry season, providing seed for seasonally based dispersal. These results suggest that the northern islands may have served as a source of colonists for the southern islands and that the pattern of aeolian inputs into an island system should be considered in other plant biogeographic studies.
Key words: aeolian, California Channel Islands, dispersal, endemism, island biogeography, plant diversity
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Introduction
MacArthur and Wilson’s (1967) equilibrium theory of island biogeography (ETIB),
originally an influential model to explain species richness on islands, remains the
accepted null model for island biogeographic studies (reviewed in Losos et al. 2010).
Just two variables, island area and distance from a source of colonists, predicts the
number of species in island biotas all over the world. Given that many different
biological phenomena, not just dispersal but also successful colonization and perhaps
speciation, are subsumed into these two variables, it is impressive that the model has been
so widely and successfully applied. The ETIB has also been effectively extended to
explain species richness on metaphorical islands like metapopulations and islands of
habitat (reviewed in Hanski 2010). DraftThis theory is especially important in the field of
conservation biogeography (Whittaker et al. 2005; Richardson and Whittaker 2010),
because protected areas are, or may ultimately be, very small areas of wild habitat
immersed in a hostile matrix, like literal islands in water.
Using the ETIB as a null model, many studies have addressed how specific factors
may impact diversity on various island systems. Inevitably, the theory does not explain
all the variation in a data set. Deviations from ETIB expectations have allowed
researchers to identify other important factors that influence the composition of island
biotas, such as nested subsets (Wright et al. 1998), order of colonization (Ricklefs and
Bermingham 2001; Gardner and Engelhardt 2008), or competition (Gardner and
Engelhardt 2008). In some studies, only one or two islands in a system deviate from
expectations based on ETIB; for example, a particular island may have more or fewer
species than expected on the basis of the model (Moody 2000). These deviations might
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be caused by something specific about a particular island that merits further investigation, such as geology, island age, the presence of predators, or human mediated disturbance.
However, deviations might also be explained by more general biotic and abiotic factors.
For example, distance from a continental source is an important component of the original model because the probability of dispersal is likely to be correlated with distance
(MacArthur and Wilson 1967). However, straight-line distance from a source of colonists, with no regard for details of geography, habitats, and dispersal vectors, may not be the best estimator for probability of successful dispersal.
The California Channel Islands, a group of eight oceanic islands located off the coast of southern California (Fig. 1), have long provided a natural laboratory for investigating the biogeography of variedDraft taxa on near-shore oceanic islands (Lyon 1886 a,
1886 b). Although the islands have been the focus of many biogeographic studies, no consistent pattern of colonization or diversification akin to the Hawaiian progression rule
(Funk and Wagner 1995) has been proposed for the archipelago. Early biogeographers, working under the assumption that the islands were continental in origin, relied on inferred ancient land bridges to explain observed patterns (Fig. 1; Garth 1967; von
Bloeker 1967; Rentz and Weismann 1973; Philbrick 1980; but see Savage 1967; Wenner and Johnson 1980). Even the more distant and isolated southern islands were assumed to have had land bridges or to be within easy and regular colonization distance from the continent and, therefore, within the routine dispersal distances of mainland taxa.
Consequently, many endemics were thought to be the relicts of former panmictic island- continental assemblages that were disrupted when the mainland populations withdrew, predominantly to the north, after the last glacial maximum (Parish 1903; Axelrod 1967;
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Muller 1967; Raven 1967; Thorne 1969; Oberbauer 2002). More recent studies (Vedder
and Howell, 1980) have clearly demonstrated that all of the Channel Islands are oceanic
in nature, having never been connected the mainland, although, during the last glacial
maximum the northern islands were only separated from the mainland by a narrow (ca. 4
km) deep-water channel (Johnson 1983; Kinlan et al. 2005; Fisher et al. 2009).
Among taxa for which land bridge colonization or relictual endemism were not
inferred, no general biogeographic patterns emerged. Several different biogeographic
predictions are suggested depending on dispersal methods and island geography. For
example, little avian differentiation might be expected because the California coastline
curves around the islands creating the Southern California Bight such that the entire
archipelago is within the flyway of Draftmany birds (Diamond 1969). Alternately, organisms
transported primarily by ocean currents would be expected to have colonization routes
mirroring the counter-clockwise path of the California Eddy (Moody 2000), while those
moved by catastrophic floods would be expected to colonize opposite the outflow of
large mainland rivers (Schoenherr et al. 2003).
Despite the complex and varied patterns that might be expected given the interplay
of these biotic and abiotic features, Moody (2000) found that Channel Island plants
conformed to the McArthur and Wilson (1967) expectations of richness and endemism.
The northern islands (San Miguel, Santa Rosa, Santa Cruz, and Anacapa), which are
relatively close (20 – 44 km) to the mainland, support rich plant biotas (191-495 native
species) with moderate endemism (mean of native flora = 10.78%; Table 1). The
generally more distant southern islands (San Nicolas, Santa Barbara, Santa Catalina, and
San Clemente; 32 – 98 km) harbor more depauperate plant biotas (87-437 native species),
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often with higher endemism (mean of native flora = 12.38%). Moody (2000) found that
Channel Island plant diversity is strongly impacted by island size and that endemic plant diversity is secondarily impacted by island isolation. However, in the analyses examining isolation, distance to the mainland explained little of the variability in endemism among all islands ( r2 = 0.17), but it explained the majority of the variability in the seven nearest islands ( r2 = 0.78, excluding San Nicolas) This strong correlation is consistent with both independent colonization of each island from mainland sources and stepping-stone colonization from adjacent islands (Fig. 1).
Few studies have addressed Channel Island colonization histories. However, studies that have investigated the source populations for southern island taxa have failed to find evidence for colonization fromDraft Santa Catalina, the largest and closest to the mainland of the southern islands. Instead, several biogeographers have inferred a northern island source for southern island invertebrates, particularly for San Nicolas
Island taxa (Weissman and Rentz 1976; Rust et al. 1985; Powell 1994; Ramirez 1995;
Chatzimanolis et al. 2010). Similarly, Riley (2012) found evidence of a north to south colonization route within the plant genus Eriogonum (Polygonaceae).
The lack of corroboration for the shortest-line distance dispersal hypothesis along with the low correlation between endemism and distance to the mainland in the complete data set in Moody’s (2000) analysis suggest that, at least for some taxa, distance to the mainland alone does not determine colonization patterns. A north to south colonization route, as inferred in the above mentioned studies, suggests dispersal by the prevailing northwesterly winds. The current wind patterns have been largely stable for the past
10,000 years (Erlandson et al. 2005; Muhs et al. 2009), a period during which the
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environment warmed and dried, favoring establishment of the modern coastal sage scrub
community (Kennett et al. 2007; Anderson et al. 2009). Circulation studies demonstrate
that the Channel Islands receive strong and steady aeolian inputs from the northwest to
the southeast throughout the spring, summer, and fall (Dong et al. 2009; Fig. 1), with the
greatest wind strength occurring across the northern islands. Beginning in the fall and
peaking in the winter, seasonal Santa Ana winds originating in the Great Basin move air
from the east, out of the Los Angeles Basin, westward onto the islands closest to the
shore (Anacapa, Santa Cruz, and Santa Catalina; Muhs et al. 2008; Raphael 2003).
Therefore, the southern islands, excepting Santa Catalina, which lies in the path of the
Santa Ana winds, receive aeolian inputs primarily from the northern islands (Dong et al.
2009; Fig. 1), minimizing the importanceDraft of the straight-line distance of these islands to
the mainland. It is likely that components of the modern biota were dispersed by the
strong prevailing or periodic Santa Ana winds, depending on the location of specific
islands. In that case, the source of colonists would be an occupied area along the axis of
the prevailing or seasonal winds, rather than the nearest occupied mainland area.
In the current work, we examined native plant diversity on the Channel Islands with
respect to flowering time, isolation, and the nestedness of species compositions among
islands. We have focused solely on native plants, because the total flora includes many
exotic taxa (49-196 per island), which are largely attributable to human introduction, not
passive colonization. Our approach sheds light on the previous analyses of Moody (2000)
examining the role of island isolation on plant diversity while explicitly accounting for
seasonal aeolian inputs, which are likely to have a significant impact on seed availability,
dispersal direction, and subsequent colonization.
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Methods
Plant diversity data for each island was obtained from Ratay et al. (2014; Table 1), which is the most current list of Channel Island plant species diversity. Although species diversity has likely been impacted by human activities on the islands (Moody 2000), no estimates of species diversity prior to human usage of the islands exist. Phenology data was obtained from the Jepson eFlora (Jepson Flora Project, 2013) for all native angiosperms. Flowering time was grouped into the following seasons: Winter (December,
January, February), Spring (March, April, May), Summer (June, July, August), and Fall
(September, October, November). Species with widespread flowering times were counted as flowering in multiple seasons. Species were classified as primarily flowering in either the Wet (>30 mm of precipitation perDraft month; November-May) or Dry (<30 mm of precipitation per month; June-October) seasons, based on 89 years (1904-1993) of rainfall data from Stanton Ranch, Santa Cruz Island (Junak et al. 1995). Because dry flowering taxa are more likely to produce seeds at the appropriate time for aeolian dispersal, all species were classified as flowering exclusively in Wet or Dry seasons based on the greatest number of months they were observed flowering. Any taxa that had an equal number of months of flowering in Wet and Dry seasons were classified as Wet season. Island Area and distance to the Mainland (DMnl ) were obtained from Moody
(2000). Distance to the nearest source (D source , Table 1) based on the autumn prevailing winds (Dong et al. 2009, Muhs et al. 2008, Raphael 2003; Fig. 1), was calculated as the straight-line distance in Google Earth (Google, Mountain View, CA). For three islands,
San Nicolas, Santa Barbara, and San Clemente, the northern islands were treated as the nearest source. All regression analysis were performed with StatPlus:mac v. 5
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(AnalystSoft Inc., Alexandria, VA). Regression analyses based on the current native plant
diversity were calculated for D Mnl and Dsource with and without San Nicolas Island to
facilitate comparison to Moody’s (2000) results. Our regression analyses have utilized
percent endemic taxa on each island to normalize the impact of island size on total
species diversity.
The level of nestedness in the island specific species assemblages was calculated
using BINMATNEST (Rodríguez-Gironés & Santamaría, 2006), which orders the rows
and columns of presence/absence data to minimize the nestedness temperature and
compares this maximally packed matrix to three alternative null models. We tested the
Species-by-Island assemblages against 1000 matrices randomly generated under the most
conservative null model (Model 3), Draftusing the recommended default parameters.
Nestedness analyses examined either all native taxa or native taxa flowering during the
dry season. Because a high proportion of endemic taxa has been shown to inflate
measures of nestedness (Greve and Chown 2006), both analyses were performed with
and without species limited to single islands. The pattern of nestedness was compared to
that of island area and distance to the nearest source by calculating Spearman’s rank
correlation in StatPlus:mac v. 5.
Results
Plant species diversity by island, and island characteristics are given in Table 1. The
previous analyses of Channel Island plant diversity by Moody (2000), utilized species
counts from Junak et al. (1995), which on average had fewer total taxa on each island
than the Ratay et al. (2014) species counts. The mean percentage of native angiosperms
flowering was lowest in winter and highest in spring, with 24%, 88%, 80%, and 34% of
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taxa flowering in winter, spring, summer, and fall, respectively (Fig. 2). More taxa where found to primarily flower in the dry season (mean = 52%) than the wet season (mean =
48%).
Number of native taxa per island is positively correlated with island area (r2 =
0.912, p < 0.001; data not shown) and the species-area residuals are positively correlated with distance to the mainland ( r2 = 0.522, p = 0.043; data not shown), confirming the previous results of Moody (2000) with the current species counts. The percent of endemic taxa in the native flora was positively correlated with modified distance to a seed source
2 (D source ; r = 0.482, p = 0.056; Fig 3A) but not straight-line distance to the mainland
2 (D mnl ; r = 0.0986, p = 0.449; data not shown). With removal of San Nicolas Islands, following the approach of Moody (2000),Draft the percent of endemic taxa in the native flora
2 2 was positively correlated with D source (r = 0.583, p = 0.046; data not shown) and Dmnl (r
= 0.492, p = 0.079; Fig 3A). An isolation effect was also observed with regard to flowering season, with the percent dry season flowering endemic taxa in the native flora
2 2 being positively correlated with D source (r = 0.665, p = 0.014; Fig 3B) but not D mnl (r =
0.155, p = 0.334; data not shown). However, there was no effect of isolation on the
2 percent of wet season flowering endemics on D source (r = 0.081, p = 0.495; data not
2 shown) or D mnl (r = 0.038, p = 0.646; data not shown).
Nestedness temperatures are calculated from maximally packed matrices, in which columns are sorted left to right, so that species on many islands are to the left, and rows are sorted top to bottom, so that islands with many species are toward the top. A perfectly nested matrix will have no empty cells in the upper left, which indicates lack of common species on a species-rich island, and no occupied cells in the lower right, which
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indicates presence of a rare species on a species-poor island. The native species and dry-
season flowering species assemblages are highly nested (p < 0.0001; Fig. 4). Nestedness
is characterized by matrix temperature, a measure of the signal to noise ratio that varies
from 0 (perfectly nested) to 100 (randomly distributed; Atmar and Patterson 1993).
Matrices that included species with single island distributions have calculated
temperatures more than 30 degrees below the expected temperatures (T obs = 16.64 and
Tobs = 16.49, for all native and dry-season flowering native species, respectively), while
the matrices excluding species with single island distributions have calculated
temperatures more than 20 degrees below the expected temperature (Fig. 4). The pattern
of nestedness is positively correlated with island size (rho = 0.91, p < 0.01), but not with
distance to the mainland or the nearestDraft source (data not shown).
Deviations from the rank order between nestedness and area are Santa Catalina,
which is higher in the maximally packed matrix for all native, but not dry-season
flowering taxa, the small northern islands of San Miguel and Anacapa, which are higher
in both matrices, and the small southern island of San Nicolas, which is lower in both
matrices. Idiosyncratically distributed species, which appear as gaps or disjunct blocks in
the matrix, may highlight species that are more strongly influenced by features other than
island area, such as dispersal corridors, competitive exclusion, or unique habitat
requirements (Atmar and Patterson 1993). Islands with notable idiosyncratic
distributions in our data include Santa Barbara, which lacks many common species and
has a relatively high proportion of more narrowly distributed species, and the large
southern islands (Santa Catalina and San Clemente), which both lack species found on
smaller islands and share species not found on larger islands (Fig. 4). Other disjunct
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blocks in the matrices are species common to the northern islands and found on isolated southern islands, like San Clemente or San Nicholas, but not on Santa Catalina (Fig. 4).
Overall, the smaller northern islands share 83.4 – 96.1% of their floras with the most species rich island, Santa Cruz. The smaller southern islands also share the majority
(70.1–72.3%), of their floras with Santa Cruz, but have floras that contain a larger proportion (14.3 – 16.3%) of species found on the large southern island of Santa Catalina, but not Santa Cruz.
Discussion
Our re-examination of the influence of isolation on floral endemism in the California
Channel Islands shows that incorporating prevailing winds improves the fit of the model
(Fig. 3A), relative to Moody (2000).Draft These analyses demonstrate that incorporating knowledge of abiotic factors, prevailing winds and flowering time in our system, can enhance understanding of the ETIB. Although the native island floras are most strongly influenced by area, as evidenced in Moody’s (2000) and our analyses, deviations from perfect nestedness and the patterns of endemic species richness indicate that other features are also important drivers of island species diversity.
In Moody’s (2000) analysis, San Clemente Island had fewer, and San Nicolas
Island had more, species than expected from the intersection of species-area and isolation curves. Furthermore, San Clemente had a higher, and San Nicolas had a lower, proportion of endemic taxa than predicted by distance from the mainland. Moody (2000) determined that if San Nicolas Island, which is the greatest outlier among the data with relatively low endemism (10.1%), was excluded, isolation explained much more of the pattern of endemism. However, when distance along the path of the dominant wind
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currents is used rather than shortest distance to the mainland, San Clemente Island is
further from, and San Nicolas Island is closer to, potential colonists than previously
calculated (Table 1; Fig. 2). Using this modified measure, distance explains much of the
variability in native floral endemism (r2 = 0. 482; Fig. 3A), without the need to remove
any observations. When considering only the endemics that flower in the dry season,
which would be more likely to be wind dispersed, the correlation is stronger (r2 = 0. 68;
Fig. 3B)
The relative importance of seasonal dispersal is also supported by flowering data
and nestedness within the flora. Classification of angiosperms into predominantly wet
and dry flowering groups indicates that the flora skews slightly towards more dry season
flowering (Fig. 2). The abundance ofDraft dry flowering angiosperms translates into dry
season seed production and the potential for dispersal events when seasonal winds are at
their strongest (Dong et al. 2009, Raphael 2003). Strong winds such as these have been
shown to be effective long distance dispersal agents, even for taxa without specific
adaptations to facilitate aeolian dispersal (Nathan 2008). Analyses of nestedness also
support seasonal dispersal because the dry-season flowering species of the southern
islands are nested subsets of the dry-season flowering species of the large northern
islands, Santa Cruz and Santa Rosa.
Although the close proximity of the Channel Islands to mainland California has
likely impacted colonization patterns among organisms with varied dispersal
mechanisms, a seasonal dispersal pattern may be common among aeolian influenced
dispersers, especially for the isolated southern islands. Future studies should test the
importance of the periodic Santa Ana winds blowing west off the mainland coupled with
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the prevailing northwesterly winds in driving colonization patterns. Our findings are limited by the small number of islands in the system, and lack of understanding of the evolutionary history of taxa and populations. Nevertheless, the results of this study demonstrate that abiotic processes, such as aeolian inputs, should be considered along with potential biotic (e.g. animal migration patterns) processes when assessing biogeographic patterns.
Acknowledgements
We are grateful to Sarah Ratay for sharing her species lists and to two anonymous reviewers for helpful comments on a previous version of the manuscript. Draft
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Literature Cited
Anderson, R.S., Starratt, S., Jass, R.M.B., and Pinter, N. 2010. Fire and vegetation history
on Santa Rosa Island, Channel Islands, and long-term environmental change in
southern California. J. Quat. Sci. 25 (5): 782–797.
Atmar, W., and Patterson, B.D. 1993. The measure of order and disorder in the
distribution of species in fragmented habitat. Oecologia 9(3): 373–382.
Axelrod, D.I. 1967. Geologic history of the California insular flora. in Proceedings of the
symposium on the biology of the California Islands . Edited by R.N. Philbrick.
Santa Barbara Botanical Gardens, Santa Barbara, CA. pp. 267–316.
Chatzimanolis, S., Norris, L.A., and Caterino, M.S. 2010. Multi-island endemicity:
phylogeography and conservationDraft of Coelus pacificus (Coleoptera: Tenebrionidae)
darkling beetles on the California Channel Islands. Ann. Entomo. Soc. Am. 103 (5):
785–795.
Diamond, J.M. 1969. Avifaunal equilibria and species turnover rates on the Channel
Islands of California. PNAS 64 (1): 57–63.
Dong, C., Idica, E.Y., and McWilliams, J.C. 2009. Circulation and multiple-scale
variability in the Southern California Bight. Prog. Oceanog. 82 (3): 168–190.
Erlandson, J.M., Rick, T.C., and Peterson, C. 2005. A geoarchaeological chronology of
Holocene dune building on San Miguel Island, California. The Holocene 15 (8):
1227–1235.
Fisher, M.A., Langenheim, V.E., Nicholson, C., Ryan, H.F., and Sliter, R.W. 2009.
Recent developments in understanding the tectonic evolution of the southern
15 https://mc06.manuscriptcentral.com/botany-pubs Botany Page 16 of 27
California offshore area: Implications for earthquake-hazard analysis. Geological
Society of America Special Papers 454 : 229–250.
Funk, V.A., and Wagner, W.L. 1995. Biogeographic patterns in the Hawaiian Islands. In
Hawaiian biogeography: evolution on a hot spot archipelago. Edited by
W.L.Wagner and V.A. Funk. Smithsonian Institution Press, Washington. pp. 379–
419.
Gardner, R.H., and Engelhardt, K.A.M. 2008. Spatial processes that maintain biodiversity
in plant populations. Perspectives in Plant Ecology, Evolution and Systematics 9(3–
4): 211–228.
Garth, J.S. 1967. Introduction to Insular Zoology. In Proceedings of the Symposium on
the Biology of the California Islands.Draft Edited by Philbrick, R.N. .Santa Barbara
Botanic Garden, Santa Barbara, CA. pp. 181–183.
Greve, M., and Chown, S.L. 2006. Endemicity biases nestedness metrics: a
demonstration, explanation and solution. Ecography 29 (3): 347–356.
Hanski, I. 2010. Ecological and genetic models of diversity: lessons across disciplines.
In,The theory of island biogeography revisited . Edited by J.B. Losos, R.E.
Ricklefs and R.H. MacArthur Princeton University Press, Princeton, NJ. pp. 186–
213.
Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html,
accessed on Oct 10, 2015.
Johnson, D.L. 1983. The California continental borderland: landbridges, watergaps and
biotic dispersals. In Quaternary Coastlines and Marine Archaeology: Towards the
16 https://mc06.manuscriptcentral.com/botany-pubs Page 17 of 27 Botany
Prehistory of Land Bridges and Continental Shelves . Edited by P.M. Masters and
N.C. Flemming. Academic Press, New York, NY. pp. 481–527.
Junak. S., Ayers, T., Scott, R., Wilken, D., and Young, D.1995. A flora of Santa Cruz
Island. Santa Barbara Botanic Garden, Santa Barbara, CA.
Kennett, D.J., Kennett, J.P., Erlandson, J.M., and Cannariato, K.G. 2007. Human
responses to Middle Holocene climate change on California's Channel Islands.
Quat. Sci. Rev. 26 (3-4): 351–367.
Kinlan, B.P., Graham, M.H., and Erlandson, J.M. 2005. Late-Quaternary changes in the
size and shape of the California Channel Islands: Implications for marine
subsidies to terrestrial communities. In Proceedings of the Sixth California Island
Symposium. Edited by D.K.Draft Garcelon and C.A. Schwemm. Santa Barbara
Museum of Natural History, Santa Barbara, CA. pp. 119–130.
Losos, J.B., Ricklefs, R.E., and MacArthur, R.H. 2010. The theory of island
biogeography revisited. Princeton University Press, Princeton, NJ.
Lyon, W.S. 1886 a. The flora of our southwestern archipelago. I. Botanical Gazette
11 :197–205.
Lyon, W.S. 1886 b. The flora of our southwestern archipelago. II. Botanical Gazette
11 :330–336.
MacArthur, R. H. and E. O. Wilson. 1967. The theory of island biogeography. Princeton
University Press, Princeton, NJ.
Moody, A. 2000. Analysis of plant species diversity with respect to island characteristics
on the Channel Islands, California. Journal of Biogeography 27 (3): 711–723.
17 https://mc06.manuscriptcentral.com/botany-pubs Botany Page 18 of 27
Muhs, D.R., Budahn, J.R., Johnson, D.L., Reheis, M., Beann, J., Skipp, G., Fisher, E.,
and Jones J.A. 2008. Geochemical evidence for airborne dust additions to soils in
Channel Islands National Park, California. Geo. Soc. Am. Bull. 120 (1-2): 106–126.
Muhs, D.R., Skipp, G., Schumann, R.R., Johnson, D.L., Mcgeehin, J.P., Beann, J.,
Freeman, J., Pearce, T.A., and Rowland, Z.M. 2009. The origin and paleoclimatic
significance of carbonate sand dunes deposited on the California Channel Islands
during the last glacial period. In Proceedings of the Seventh California Islands
Symposium. Edited by C.C. Damiani and D.K. Garcelon. Institute for Wildlife
Studies , Arcata, CA. pp. 3–14.
Muller, C.H. 1967 Relictual origins of insular endemics in Quercus . in Proceedings of the
symposium on the biology of Draftthe California Islands . Edited by R.N. Philbrick.
Santa Barbara Botanical Gardens, Santa Barbara, CA. pp. 73–77.
Nathan, R. 2006. Long distance dispersal of plants. Science. 313 (5788): 786–788.
Oberbauer, T. 2002. Analysis of vascular plant species diversity of the Pacific Coast
islands of Alta and Baja California. In Proceedings of the Fifth California Islands
Symposium. Edited by D.R. Browne, K.L. Mitchell and H.W. Chaney. Santa
Barbara Museum of Natural History, Santa Barbara, CA. pp. 201–211.
Parish, S.B. 1903 A sketch of the flora of Southern California (concluded). Botanical
Gazette 36 : 259–279.
Philbrick, R. 1980. Distribution and evolution of endemic plants of the California Islands.
In The California Islands: proceedings of a multidisciplinary symposium. Edited by
D.M. Power. Santa Barbara Museum of Natural History, Santa Barbara, CA. pp.
173–188.
18 https://mc06.manuscriptcentral.com/botany-pubs Page 19 of 27 Botany
Powell, J.A. 1994. Biogeography of Lepidoptera on the California Channel Islands. In
The Fourth California Islands Symposium: Update on the Status of Resources.
Edited by W.L. Halvorson and G.L. Maender. Santa Barbara Museum of Natural
History, Santa Barbara, CA. pp. 449–464.
Ramirez, M.G., and Beckwitt, R.D. 1995. Phylogeny and historical biogeography of the
spider genus Lutica (Araneae, Zodariidae). Journal of Arachnology 23 (3): 177–193.
Raphael, M.N. 2003. The Santa Ana winds of California. Earth Interactions 7(8): 1–13.
Ratay, S.E., Vanderplank, S.E., and Wilder, B.T. 2014. Island specialists: shared flora of
the Alta and Baja California Pacific Islands. Monographs of the Western North
American Naturalist 7: 161–220.
Raven, P.H. 1967. The floristics of Draftthe California Islands. In Proceedings of the
symposium on the biology of the California Islands . Edited by R.N. Philbrick.
Santa Barbara Botanical Gardens, Santa Barbara, CA. pp. 57–67.
Rentz, D.C., and Weissman, D.B. 1973. The origins and affinities of the Orthoptera of the
Channel Islands and adjacent mainland California. Part I. The Genus Cnemotettix .
Proc. Acad. Nat. Sci. Philadelphia 125 (6): 89–120.
Ricklefs, R.E., and Bermingham, E. 2001. Nonequilibrium diversity dynamics of the
Lesser Antillean Avifauna. Science 294 (5546): 1522–1524.
Richardson, D.M., and Whittaker, R.J. 2010. Conservation Biogeography – foundations,
concepts and challenges. Diversity and Distributions 16 (3): 313–320.
Riley, L. 2012. Comparative phylogeography of California Channel Island endemic
Eriogonum (Polygonaceae). University of South Dakota. ProQuest Dissertations
and Theses, Retrieved from http://search.proquest.com
19 https://mc06.manuscriptcentral.com/botany-pubs Botany Page 20 of 27
Rodríguez-Gironés, M. A. and L. Santamaría. 2006. A new algorithm to calculate the
nestedness temperature of presence-absence matrices. Journal of Biogeography, 33:
924–935.
Rust, R., Menke, A., and Miller, D. 1985. A biogeographic comparison of the bees,
sphecid wasps, and mealybugs of the California Channel Islands (Hymenoptera,
Homoptera). In Entomology of the Channel Islands: Proceedings of the First
Symposium. Edited by A. Menke and D. Miller. Santa Barbara Museum of Natural
History, Santa Barbara, CA. pp. 29–59.
Savage, J.M. 1967. Evolution of the insular herpetofaunas. In Proceedings of the
symposium on the biology of the California Islands . Edited by R.N. Philbrick.
Santa Barbara Botanical Gardens,Draft Santa Barbara, CA. pp. 219–227.
Schoenherr, A.A., Feldmeth, C.R., and Emerson, M.J. 2003. Natural History of the
Islands of California. Taylor & Francis, US.
Thorne, R.F. 1969 The California Islands. Annals of the Missouri Botanical Garden 56 :
391–408.
Vedder, J.G., and Howell, D.G. 1980. Topographic evolution of the Southern California
Borderland during late Cenozoic time. In The California Islands: proceedings of a
multidisciplinary symposium. Edited by D.M. Power. Santa Barbara Museum of
Natural History, Santa Barbara, CA. pp. 7–31. von Bloeker, J.C. Jr, 1967. Land mammals of the southern California islands. in
Proceedings of the symposium on the biology of the California Islands . Edited by
R.N. Philbrick. Santa Barbara Botanical Gardens, Santa Barbara, CA. pp. 245–266.
20 https://mc06.manuscriptcentral.com/botany-pubs Page 21 of 27 Botany
Weissman, D.B., and Rentz, D.C. 1976. Zoogeography of the grasshoppers and their
relatives (Orthoptera) on the California Channel Islands. Journal of Biogeography
3(2): 105–114.
Wenner, A.M., and Johnson, D.L. 1980. Land vertebrates on the California Channel
Islands: sweepstakes or bridges? In The California Islands: proceedings of a
multidisciplinary symposium. Edited by D.M. Power. Santa Barbara Museum of
Natural History, Santa Barbara, CA. pp. 497–530.
Whittaker, R.J., Araujo, M.B., Jepson, P., Ladle, R.J., Watson, J.E.M., and Willis, K.J.
2010. Conservation Biogeography: assessment and prospect. Diversity and
Distributions 11 (1): 3–23.
Wright, D.H., Patterson, B.D., Mikkelson,Draft G.M., Cutler, A., and Atmar, W. 1998. A
comparative analysis of nested subsets of species composition. Oceologia 113 (1):
1–20.
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Table 1. California Channel Island names, codes, and characteristics.
2 Code Area (km ) NTot NNat NEnd DMn l (km) Source DSource (km) Santa Barbara BAR 2.6 135 87 13 61 Northern CCI 82 Anacapa ANA 2.9 262 191 24 20 Mainland CA 20 San Miguel MIG 37 291 213 19 42 Mainland CA 42 San Nicolas NIC 58 275 158 16 98 Northern CCI 76 San Clemente CLE 145 436 303 47 79 Northern CCI 145 Santa Catalina CAT 194 617 437 39 32 Mainland CA 32 Santa Rosa ROS 217 500 399 46 44 Mainland CA 44 Santa Cruz CRU 294 636 485 49 30 Mainland CA 30
Table Notes. Area and distance to mainland California (D Mnl ), from Moody (2000); number of total plant taxa (N Tot ), number of native plant taxa (N Nat ), and number of endemic plant taxa (N End ) from Ratay et al. (2014); the inferred location of the nearest large population of potential aeolian colonists (Source), as either the northern California
Channel Islands (CCI) or mainland DraftCalifornia (CA), depending on which lies closer along the direction of prevailing (Dong et al. 2009) or seasonal Santa Ana winds
(Raphael 2003, Muhs et al. 2008); and the distance to the inferred location of the nearest large population of potential aeolian colonists (D Source ) as straight-line distance to nearest source along direction of prevailing or seasonal Santa Ana winds calculated in Google
Earth (Google).
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Fig. 1. Location of the California Channel Islands in the Southern California Bight
indicating the direction of prevailing northwesterly winds (black solid arrows; Dong et al.
2009) and annual Santa Ana winds (dashed gray arrows; Muhs et al. 2008; Raphael
2003).
Fig. 2. Number of native flowering angiosperms by season and percentage of native
species that flower in Wet (>30 mm of precipitation per month; November-May) or Dry
(<30 mm of precipitation per month; June-October) seasons for each of the California
Channel Islands. Island abbreviations are given in Table 1.
Fig. 3. Regression of percent of (A) total endemic and (B) dry season flowering
endemic species in the native flora of the California Channel Islands on geographic
distance to a source of colonists. DraftBlack diamonds and black solid lines calculated as
distance along the axis of prevailing winds (D source ; Table 1). Gray diamonds and
gray dashed lined calculated shortest distance to mainland (D Mnl ; Table 1), excluding
San Nicolas Island (open gray diamond). Island abbreviations are given in Table 1.
Fig. 4. Maximally packed matrix of native (above) and dry-season flowering native
(below) plant taxa, excluding taxa reported from a single island. Shading
differentiates among species distributed evenly among both the northern island and
southern islands (medium gray) and species with predominantly southern (light
gray) or northern (dark gray) island distributions. Island abbreviations are given in
Table 1.
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Draft
Fig. 1. Location of the California Channel Islands in the Southern California Bight indicating the direction of prevailing northwesterly winds (black solid arrows; Dong et al. 2009) and annual Santa Ana winds (dashed gray arrows; Muhs et al. 2008; Raphael 2003).
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Draft
Fig. 2. Number of native flowering angiosperms by season and percentage of native species that flower in Wet (>30 mm of precipitation per month; November-May) or Dry (<30 mm of precipitation per month; June-October) seasons for each of the California Channel Islands. Island abbreviations are given in Table 1. 181x219mm (300 x 300 DPI)
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Draft
Fig. 3. Regression of percent of (A) total endemic and (B) dry season flowering endemic species in the native flora of the California Channel Islands on geographic distance to a source of colonists. Black diamonds and black solid lines calculated as distance along the axis of prevailing winds (D source ; Table 1). Gray diamonds and gray dashed lined calculated shortest distance to mainland (D Mnl ; Table 1), excluding San Nicolas Island (open gray diamond). Island abbreviations are given in Table 1. 127x168mm (300 x 300 DPI)
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Fig. 4. Maximally packed matrix of native (above) and dry-season flowering native (below) plant taxa, excluding taxa reported from a single island. Shading differentiates among species distributed evenly among both t he northern island and southern islands (medium gray) and species with predominantly southern (light gray) or northern (dark gray) island distributions. Island abbreviations are given in Table 1. 155x70mm (300 x 300 DPI) Draft
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