National Park Service White Sands Department of the Interior White Sands National Monument Evolution in Action: White Animals at White Sands

here has been dramatic convergent evolution of light coloration for many of the animals which inhabit the stark Twhite gypsum dunes of White Sands National Monument. A number of different animal groups (including insects, spiders, toads, lizards, mammals) have blanched coloration on the white dunes and dark coloration in the surrounding dark desert soils (see Table 1). The gypsum sands are geologically recent, formed since the end of the last glaciation. Because of the young age of White Sands, we know that animals with lighter coloration have adapted to their environment quickly, as a result of strong natural selection. White Sands is therefore a dramatic showcase for evolution in action. The rapid, convergent evolution of blanched coloration in many species experiencing the same environment allows us to ask several important questions about the role of natural selection in generating biological diversity.

Why did light coloration evolve? Natural selection for substrate matching

Animals become better adapted to environment and had more offspring Particularly for small diurnal animals, their environment by a process called than the darker lizards. Because the we would expect strong selection for natural selection. Traits that increase light-colored individuals were more substrate matching to avoid being an individual’s reproductive success likely to survive and reproduce, the seen by visual predators. Although by improving its fit to the environment frequency of light-colored lizards no studies have directly measured tend to spread in a population. Light would increase in the next generation. predation intensity on White Sands coloration could evolve through natural After many generations of selection animals, many researchers have shown selection in dune animals if individuals for lighter individuals, the population that well-camouflaged animals are with light-coloration survived better or could eventually become white. less likely to be taken by predators reproduced more than individuals with But why would lighter individuals (Kiltie, 1992). Avian predators, such dark coloration. Imagine a population survive and reproduce better on as roadrunners and shrikes likely of dark colored lizards moving from the the gypsum dunes? There are two represent a significant threat for small brown desert soil into the white dunes. primary hypotheses for why natural animals at White Sands. Camouflage, Assume there is natural variation in selection would favor light individuals: or crypsis, is therefore essential for color in lizard populations, some camouflage and thermoregulation. survival. Even nocturnal animals can individuals being slightly darker and Natural selection for camouflage is the benefit from matching their habitat, some slightly lighter. Also assume that most likely explanation for the light because many nocturnal predators use coloration is heritable, with offspring coloration observed at White Sands vision to find prey illuminated inheriting their color pattern from but the effects of light coloration on Lowe, 1964). Also, predators can their parents. Suppose that the lighter thermoregulation require further benefit from matching their substrate individuals survived better in this new study. as to avoid detection by prey. Natural selection for thermoregulation

Another possibility is that lighter coloration has evolved for thermoregulation. Lighter-colored individuals that are active during the day may be better able to regulate body temperature because they reflect more of the intense desert sunlight (Benson, 1933). However, many of the white animals are nocturnal, so regulating absorption of the sun’s rays would not be an important selective factor. Additionally, there is no evidence that temperatures at White Sands are any more intense than in the surrounding dark soil habitat. In Color variation of earless lizard and bleached earless lizard in their environments fact, air and substrate temperatures at White Sands are actually lower for flexible coloration must have been an animal white. The only species than on the dark soils (Hager 2000, more likely to survive, reproduce, for which this appears likely is the Rosenblum unpublished). Hager even and pass their flexible-color genes on white lycosid spider (Table 2), which suggests that lighter colored lizards to their offspring. Bugbee (1942) described as “brown are at a disadvantage because they Third, it is possible that light in basic color but its abdomen usually cannot warm as quickly as their dark coloration did not evolve through appeared as if covered with hoar- soil counterparts. Although substrate natural selection but is simply picked frost.” Because “this white color was temperatures are not unusually high at up from the environment. Color can easily rubbed off when individual White Sands, it is still possible that large be picked up from the environment specimens were handled,” it is heat loads are imposed on animals either from dietary pigments (i.e.: possible that the white color is derived because of the reflective properties of pigments acquired from the food from external substances. However, gypsum. Further study is necessary, cause an animal to become white) it is also possible that the substance but current evidence is most consistent or from direct accumulation (i.e.: that is easily rubbed off is deposited with light coloration as an adaptation gypsum sand on the skin makes an by the spider and is internally for camouflage not thermoregulation. animal appear white). The third derived. Since light coloration possibility, that light color is acquired is unlikely to be derived directly What mechanism produces directly from the environment, from the environment, we must white coloration? is unlikely for most White Sand differentiate between the remaining species. First of all, light coloration two hypotheses: that individual color There are three possible mechanisms is probably not caused by diet. There is fixed or that individuals are able to explain how light coloration is are pigments which are known to to change their color to match their produced in White Sands animals. be acquired from the diet in birds current substrate. These predictions First, light coloration may be fixed for and reptiles. However these dietary have been most thoroughly tested in each individual from birth. For fixed pigments (called carotenoids) result lizards. coloration to evolve, lighter-colored in yellow and red, not blanched, animals must have been more likely coloration. to survive, reproduce, and pass their Second, Benson (1933) argued light-color genes on to their offspring. that it is unlikely for herbivorous Second, individuals may be able to animals to turn white from ingesting change color during their lifetimes certain plants. Plants at White to match their current substrate. Sands are similar to plants present Changing color in response to the in other areas of the Tularosa Basin environment is a type of phenotypic and probably take up substances plasticity and is known to occur in similar to those growing in alkaline other animals such as chameleons soils elsewhere. It is still possible and anoles. For such a mechanism to that direct accumulation of gypsum White Sands collared lizard evolve, individuals with genes coding dust or sand on the skin could turn Coloration in lizards or flexible in the bleached earless in response to temperature. She lizard (H. maculata). He collected collected white and non-white Many species of lizards are able to white lizards from the dunes and individuals from all three lizard quickly change their color in response non-white individuals from areas species which inhabit the gypsum to external and internal conditions, near the dunes. He photographed dunes (H. maculata, S. undulatus including temperature, exposure all animals to record their color and and A. inornata). She exposed the to light, and individual health and then placed them into laboratory lizards to hot and cold temperatures excitatory state (Smith, 1946; Norris cages with either white quartz sand and used a spectrophotometer to 1965). Some lizards, like chameleons or finely ground black cinders. None quantify coloration. All three lizard and anoles, can even change color of the lizards in Bundy’s experiment species did become slightly darker to more closely match their current changed colors to match the ground with colder temperatures. However, substrate. These rapid color changes color in their cages. even when cold, white lizards never are termed physiological plasticity become as dark as dark lizards. and occur as reptiles shift the Therefore rapid color change in distribution of pigments between response to the environment cannot different cell layers. Melanin, the explain observed light coloration pigment responsible for overall (Table 2). body darkness, is located in Rosenblum then tested whether melanophore cells. Melanophore color is fixed throughout a lizard’s cells are distributed several layers lifetime. She collected gravid below the surface of the skin but (pregnant) females from H. also have dendritic processes which maculata and S. undulatus from reach just below the inner surface the gypsum dunes and from nearby of the skin. Reptiles can darken dark soil habitats. She raised the or lighten in color by dispersing or eggs and newborn hatchlings aggregating melanin granules along Bleached earless lizard from light mothers and from dark these dendritic processes (Bagnara mothers in identical conditions. and Hadley, 1973). Although the lizards did change This “common-garden” experiment Scientists have been investigating color with temperature, as described removes environmental differences color change in White Sand lizards above, the White Sands lizards never as an explanation for color variation. for nearly 50 years. Some early got as dark as the darker lizards. Smith She found that hatchlings had the results suggested that White Sand (1943) and Lowe and Norris (1956) same coloration as their mothers lizards could change color, to a also held bleached earless lizards even when they were raised in the lab limited extent, with environmental in the laboratory with different- on intermediately-colored substrate. stimuli. Bundy (1955) found that colored sands. The lizards in those This provides strong evidence that bleached earless lizards (Holbrookia experiments also failed to change light coloration is fixed in these maculata ruthveni) held in the color to match the color of their species (Table 2). laboratory got slightly darker at cold current substrate. Similarly, Cowles temperatures and slightly lighter at prairie lizards (S. undulatus) and hot temperatures. Similarly, Lowe little striped whiptails (Aspidoscelis and Norris (1956) found that Cowles inornata, formerly Cnemidophorus prairie lizards (Sceloporus undulatus inornatus) held in the laboratory for cowlesi) darkened slightly when up to two years did not change color cold. These rapid color changes in (Lowe and Norris, 1956). response to temperature may help These early experiments suggest the lizards regulate temperature by that the lighter-colored lizards have increasing heat absorption when the genes that code for fixed light color animal is cold and decreasing it when and that, unlike chameleons and the animal is hot. anoles, they do not change color Early experiments also suggested to match their current background that rapid color change could not (Table 2). More recently, Rosenblum account for the dramatic blanched repeated these experiments in a coloration observed in White Sands more controlled fashion (in review). lizards. Bundy (1955) attempted to First, she evaluated the ability of Eastern fence lizard at White Sands lizards to change color rapidly determine whether color was fixed Revised 10/20/12 Although the mice molted several Further evidence that color is times in the lab, individual color was fixed in White Sands lizards comes fixed. Thus, malpais pocket mice, from studying a gene called the and possibly white sands pocket melanocortin-1 receptor gene mice, seem unable to change color to (Mc1r). This gene is known to be match their substrate (Table 2). involved in melanin production in In insects, color is usually mammals and birds. Rosenblum determined by the amount or type (2004) studied this gene in White of pigment deposited in the cuticle Sands lizards and found variation and epidermis. Like mammals, at the Mc1r gene to be associated insects could hypothetically change with color variation in the little color between molts by changing striped whiptail lizard A. inornata. the amount or type of pigment. In This study not only shows that Spadefoot toad fact color changes between molts light coloration has a genetic basis are known to facilitate camouflage white except for black eyes and but actually identifies the single in some insects (Chapman, 1969). black marks on the under-side of gene that is likely responsible for Other insects can also change their the hind feet.” When they brought blanched coloration in this species color over the short term (e.g., from these toads into the laboratory, they (Table 2). day to night) by moving pigment in gradually darkened to “the color epidermal cells closer to or further typical of the species.” Thus, these from the exterior (Chapman, 1969). toads appear to match the color of their current substrate by quickly changing color rather than having fixed white coloration (Table 2). In mammals, fur color is determined by the amount of pigment in the hairs. Once the pigment is deposited in each hair, fur color cannot be changed until the current coat is molted and replaced by another coat. However, even between molts, dune-field Striped whiptail lizards display color variation mammals may not change color to Coloration in other dune field match their current background. animals Benson (1933) collected dark- colored pocket mice (Perognathus There have been few attempts to intermedius rupestris) from the distinguish between the alternative Valley of Fires malpais and held them mechanisms for color change in in the laboratory for several years white species other than lizards. on differently-colored substrates. Mantled toothpick grasshopper However, some observational evidence, and an understanding of Such short-term color changes the mechanisms of color deposition typically occur in response to light in different taxa, suggests the likely or temperature. No one has reared mechanisms of color change for white insects from White Sands some other dune-field animals under controlled conditions with (Table 2). Some amphibians, like different-colored substrates, so it reptiles, can quickly change color to is too early to conclude whether match their current substrate (Zim color is fixed or flexible in these and Smith, 1987). Consistent with insects. Stroud (1950) did report this general phenomenon, Stroud on color changes in three insects, and Strohecker (1949) reported suggesting that the white insects that the spadefoot toads they caught use two different mechanisms to become white. He reports that the on the dunes were “completely Apache pocket mouse white locust Cibolacris parviceps Why are some dune field Lack of genetic variation arida at White Sands is “said to be animals not white? able to change its color from one In species without light coloration, instant to the next in accordance Although some populations of it is possible that there was simply with the color of the substrate” (p. dune-field animals display lighter no genetic variation for color upon 676). This report is consistent with coloration than their dark soil which natural selection could act. Chapman’s general observation that neighbors, many animals that live in Natural selection can only produce “the colours of grasshoppers and the dunes are not unusually colored. a better fit between an organism related insects tend to have a general Among insects, for example, Stroud and its environment if the trait is resemblance to the prevailing colour (1950) noted that “the absence genetically transmitted to offspring of the environment...and a change in of adaptation to the soil color is and if there is variation for the the environment leads to a change in more striking than its presence”. trait. Take the example of if light the colour of the insect.” In contrast, He collected 343 insect species coloration caused by gypsum sand Stroud (1950) suggests that the color at eight different collecting sites grains adhering to an animal’s fur. In of the two white camel crickets at within the dunes, and only four of this case there is no genetic basis for White Sands is probably fixed as a those species were lighter colored the light coloration, and offspring of result of genetic differences between than expected (Table 1). Similarly, lighter-colored individuals would the white and the related brown Blair (1943) trapped twenty-three not also be lighter-colored. Take subspecies. However, Stroud did not different species of mammals in the another example of a population cite evidence to back up his reports, dunes, and only three were lighter colonizing the gypsum dunes all so it is not clear how he justifies these colored than expected (Table 1). being exactly identical in color. In conclusions. The absence of light coloration in this case, natural selection would these species raises the question have no variation on which to act. of why light coloration has not In White Sand lizards we know evolved more often. There are three that color traits have a genetic basis primary hypotheses to explain the (see above), however in many other lack of light coloration in many groups more study is necessary animals on the dunes: insufficient before rejecting the insufficient genetic variation, differentgenetic variation hypothesis. experience of selection pressures, and constraining effects of gene Different selection pressures flow. More research is necessary to It is possible that different species Hebard’s desert grasshopper determine the relative importance of different explanations of why experience different selection From the available evidence, light coloration is relatively rare in pressures at White Sands. This white animals in the dunes appear animals inhabiting the dunes. hypothesis could apply in a number to use all three mechanisms of of different contexts: some species color change (Table 2). The white may experience weaker or stronger spiders may derive their light color selection for substrate matching, from the substrate itself. The toad, some species may experience trade- and possibly some insects, may offs between selection for crypsis change color to match their current and thermoregulation, and some environment. The lizards and species may have defenses other mammals seem to have individually than light color against predation. fixed color that likely evolved in First, lighter coloration could be response to selection pressure for slower to evolve in species where substrate-matching. Controlled the benefit of being lighter is lower experiments with more dune-field (i.e., less intensity of selection). For animals are necessary to test whether example, large nocturnal predators individuals held in the laboratory like kit fox may benefit less from change color to match their substrate being camouflaged to the white and to determine whether white sands than would a small mouse or individuals bred in the laboratory lizard, because the larger predators Kangaroo rat have white offspring. have few visually-hunting predators of their own. Note, though, that it Second, lighter color may be is possible that predators would be slower to evolve in species in better able to sneak up on unwary which light coloration yields some prey if they, too, blended in with benefits and dark coloration yields the habitat. others (i.e., opposing selective pressures or trade-offs). Especially for ectothermic (cold-blooded) organisms like lizards and insects, darker animals can absorb heat more quickly than lighter-colored animals and therefore reach their optimal activity temperature more quickly. For example, we know that White Sands lizards can never get as dark in color as their counterparts that live on dark soil. Darkling beetle Local adaptation to White Sands Gene flow constraining adaptation Kit fox may therefore reduce temperature- Also, lighter color may be slower regulation benefits from darker Finally, if there is dispersal to evolve in species that spend less coloration. If it takes lighter between populations in different time moving around on the open lizards longer to warm up in the habitats, gene flow may constrain sands and therefore benefit less from morning or if they must maintain local adaptation. When there is being camouflaged to the sands. lower activity temperatures, it may gene flow between populations For example, the bleached earless compromise their ability to forage under different selective pressures, lizard (H. maculata) forages in the for food or escape from predators. genes favored in one habitat open on the sand, while the Cowles Thus, camouflage coloration(e.g.: dark coloration genes in the prairie lizard (S. undulatus) forages may not have evolved in some desert surrounding the dunes) can primarily in darker vegetation (Hager ectothermic animals if the benefits inundate another habitat. Such 2001). Because of these differences of dark coloration for facilitating gene flow can reduce the chance in foraging ecology, the Cowles temperature regulation outweigh that individuals on the gypsum prairie lizard probably benefitsthe benefits of camouflage. dunes become adapted to their less from being camouflaged to the Third, light coloration may not local environment, even for species white sands of the open dunes. This have evolved in some species where light coloration is beneficial. may help explain why the bleached because they have other means of The extent of gene flow between earless lizard is much lighter-colored defending against predators and do dunes and non-dunes populations than is the Cowles prairie lizard not need camouflage. For example, does seem to predict the extent (Dixon, 1967). the black darkling beetle makes of camouflage coloration in some itself obvious as it marches across lizards, mammals, and insects. the white sands in the middle of the In lizards, both classic and recent day, so it seems surprising that it work suggests that gene flow has not adopted white camouflage may hinder local adaptation coloration. However, its common of dunes populations. Dixon name, the stinkbug, hints at why it (1967) documented that dunes does not need to be camouflaged. populations of the bleached If they are threatened, these beetles earless lizard (H. maculata) were stand on their heads and, if the isolated from the nearest dark threat continues, spray chemicals soil population (located 29 km that make them an unappealing southeast), whereas there were meal for predators. Some other populations of Cowles prairie lizard species that do not have camouflage (S. undulatus) immediately outside coloration may also have other of the dune field. He hypothesized kinds of defenses that protect that gene flow could explain why them against predators and make the bleached earless lizard is lighter Cowles prairie lizard camouflage unnecessary. colored than the Cowles prairie lizard. Rosenblum (in review) has Of these five species, only one Can natural selection tested this hypothesis with modern (20%), the spotted ground squirrel at White Sands lead to methods for all three White Sand (Spermophilus spilosoma), has lizards. She measured lizard color evolved lighter color. In contrast, speciation? with a spectrophotometer and of the four species that are isolated The dune field can be considered levels of gene flow using molecular from non-dunes populations, two a sand island in a sea of desert. markers. She found that the bleached species (50%) have evolved white Just as oceanic islands often have earless lizard is lighter in color and or lighter color, the Apache pocket unusual species that are not found better substrate-matched than either mouse (Perognathus flavescens elsewhere, islands of habitat like the the Cowles prairie lizard or the little apachii) and the southern plains White Sands dune field can also have striped whiptail. Furthermore, this woodrat (Neotoma micropus species not found elsewhere. Species corresponds exactly to observed leucophaea). Although sample that are restricted geographically levels of gene flow; there is more gene sizes are quite small and modern to one or a few localities are called flow between dark soil and white methods were not used to endemic species. Endemic forms sand populations for the Cowles measure gene flow, these data can evolve fairly quickly if they prairie lizard and the little striped do at least suggest that mammals are geographically or genetically whiptail than for the bleached that are isolated in the dunes are isolated and if they are exposed earless lizard. This suggests that the more likely to develop camouflage to unique selection pressures. But degree of genetic isolation of dune coloration. can selection for local adaptation populations may be very important actually lead to speciation? Again, in determining the outcome of we have preliminary data on this natural selection. question for White Sands lizards, Differences in the extent of gene but more research is necessary for flow between populations may other taxa. also explain coloration patterns in dune-field mammals. Both Benson (1933) and Blair (1943) noted that species that were isolated on the white sands were more likely to have evolved camouflage coloration than species that had populations in the White Sands camel cricket surrounding area. The same is true Finally, the two camouflaged camel of dark-colored animals living on crickets in the dunes apparently the black lava at the Valley of Fires differ in both the extent of gene malpais. Of the nine small mammals flow between dunes and non-dunes trapped by Blair (1943) within the populations and in the extent to White moth found at White Sands dune field, five species are probably which most animals within the not reproductively isolated from dunes have colors that match the Mate choice and reproductive non-dunes populations, because white sands. Ammobaenites were isolation there are animals living in the quartz not collected at the eleven collecting sands surrounding the dunes. localities immediately outside One mechanism by which natural of the dunes, but Daihinoides selection can lead to reproductive were collected at sites outside of isolation is when traits important in the dunes. As expected if these local adaptation are also important differences in gene flow affect the for mate choice. For example, if ability of the dunes populations lighter lizards prefer to mate with to evolve camouflage coloration, other light lizards, there may be an all of the collected Ammobaenites interaction between natural and were white, while the collected sexual selection. But do lizards really Daihinoides “vary in coloration from choose mates based on their color? brown individuals to individuals Dorsal coloration is not known to be which show considerable pigment important for mate choice, but lizards reduction” (Stroud and Strohecker, have other color patches which are Spotted ground squirrel 1949, p. 126). used for communication and mate Defining species at White Sands choice. These signaling colors are head color is important for usually bright yellow, red or blue and communication, and again there At this time, none of the White actually can be affected by changes are differences between White Sands animals are considered new in melanin production. Since White Sands and dark soil individuals. species. However, six subspecies Sands lizards produce less melanin, Differences in signaling coloration (Table 1) are restricted to the there may be a connection between and mating preference between dune field and therefore could be natural selection and sexual selection dune and non-dune populations considered endemic. The number for lizards at White Sands. do not necessarily mean that dune populations are reproductively of endemic subspecies or species isolated. However, it means that depends on how species and the raw material is available for subspecies are defined, an area sexual selection. of great debate in evolutionary Ideally, we would like to test biology. Most of the taxonomic mate choice directly. Rosenblum work on dune-field animals (in prep) was able to do this with was done many years ago, and the bleached earless lizard (H. application of modern taxonomic maculata), the lizard that is most techniques could help to clarify the highly-adapted to the gypsum status of endemic forms at White environment. She conducted a Sands. number of different mate-choice One area of increasing interest experiments to see if White Sands for evolutionary biologists is how females preferred to mate with to define units for conservation. light males or dark males. In fact, Although forms at White Sands light females did have a preference may not be unique species, some for light males. Furthermore, might be considered Evolutionary she found morphological Significant Units or Management differences between White Sand Units (ESUs or MUs, sensu Moritz and dark soil populations of H. 1994). These designations help maculata. In addition to their scientists and managers consider blanched coloration, White what unique evolutionary processes Sand populations are unique in have occurred over a given the shape of their bodies, their landscape. Recent studies have Greater earless lizard heads and their feet. These shown that landscapes like White morphological differences could Sands in which there is a dramatic Several studies have now shown that be further specializations to the change in the environment (termed lizards on and off the dunes show sandy environment. Again, these ecotones) are especially important differences in signaling colors. Both results do not necessarily mean in generating biological diversity. Hager (2001) and Rosenblum (in that White Sands bleached earless Conserving ecotones may allow prep) have documented differences lizards should be considered a us to protect species that already in signaling colors between White new species, but the extensive exist while allowing new species Sands and dark soil populations differences between dune and to evolve. Ultimately, White Sands of the bleached earless lizard (H. non-dune populations suggest can be a classroom for the study of maculata). Female lizards of this that natural selection at White evolution in action and a natural species have bright yellow, orange Sands could lead to reproductive laboratory for conserving our and red markings on their throats and isolation. biological resources. sides which are used to communicate during the breeding season. Rosenblum also found differences in signaling colors for the other two White Sand lizard species. For the Cowles prairie lizard (S. undulatus), males have bright blue colors on their bellies which are different in dune and non-dune populations. For the little striped whiptail (A. inornata), Ecotone Table 1: Description of the species reported to have light-colored populations on the gypsum dune fields of White Sands National Monument.

Species Description of coloration Source

Reptiles “The dorsal color...is a light, gray- Bundy, 1955 Bleached earless lizard ish cream, more yellowish on the Dixon, 1967 (Holbrookia maculata sides....Under the microscope no Lewis, 1949 subspecies ruthveni)1 pigment granules are discernible Smith, 1943 except on the sides of the belly, where on each side two small, black spots are formed by a concentration of dark pigment granules” (p. 343, Smith, 1943).

Cowles prairie lizard “On the middorsal surface of the Dixon, 1967 (Sceloporus undulatus body there is a broad light blue Lowe & Norris, 1956 subspecies cowlesi)2 stripe” from the head to the base of the tail. “This wide light blue stripe is bordered on either side by com- plete light tan...stripes” alternating with white stripes. The top of the tail is bluish towards the base and grades into pale gray towards the tip. The underside of the tail “is pure white.” (p. 127, Lowe and Norris, 1956)

Little striped Whiptail Color “is strikingly different from Dixon, 1967 (Aspidoscelis inornata, formerly typical normal colored samples from Cnemidophorus inornatus) southern New Mexico.” In Las Cruces, the ground color is “dark brown to chocolate brown with the 7 white lines greatly contrast- ing against the dark ground color.” (p. 17). In dunes populations, “the ground color is pale yellowish-gray to pale bluish-gray with the 6 to 7 light stripes present but somewhat obscure. The limbs are pale blue without a suffusion of grayish bars on the dorsal surfaces in most speci- mens. The head is light brown to gray-blue in females, bright sky-blue to blue in males” (pp. 16-17, Lowe and Norris, 1956).

Amphibians “completely white except for black Stroud, 1949 Spadefoot toad eyes and black marks on the under- (Scaphiopus couchii) side of the hind feet.” (p. 232)

Fur color ranges “from white almost Benson, 1933 Mammals to the yellow color normally found Apache pocket mouse in apache pocket mice. The majority (Perognathus flavescens are nearly white and match the color subspecies apachii)1, 3 of the background very well.” (p. 27, Benson, 1933) Species Description of coloration Source

White sands wood rat “Upper parts pale ashy gray or near Goldman, 1933 (Neotoma micropus pale smoke gray, purest on cheeks, subspecies leucophaea)1, 4 shoulders, and sides, the top of head and back thinly mixed with black producing a finely lined effect; under parts white.” (p. 472, Goldman, 1933

Spotted ground squirrel “somewhat paler than the Alamogor- Blair, 1941 Source (Spermophilus spilosoma) do specimens.” (p. 220, Blair, 1941).

Insects Camel cricket “Wholly colorless,...a translucent Stroud, 1950 (Ammobaenites phrixocnemoides white..., the eyes are black and the subspecies arenicolus)1 spurs and spines are reddish but un- pigmented.” (p. 242).

Camel cricket “Entirely white and the light color Bugbee, 1942 (Daihinoides hastiferum must be due to a lack of any pigment Stroud, 1950 subspecies larvale)1 as one can see through the epidermis Stroud & Strohecker, 1949 and observe internal organs” (Bugbee, 1942).

Locustid “Reddish brown specimens were Stroud, 1950 (Cibolacris parviceps arida) taken on red soil near La Luz, but those from the White Sands dunes area were very light in color” (p. 676).

Tiger beetle Some beetles “were very near the Stroud, 1950 (Cicindela praetextata) typical form but others have very broad white margins covering more than half the elytra” (p. 676).

Arachnids “brown in basic color but its abdo- Bugbee, 1942 Lycosid spider men usually appeared as if covered with hoar-frost. This white color was easily rubbed off when individual specimens were handled.”

Scorpion “light-colored” Bugbee, 1942 (Vejovis boreus)

Solpugid “white in color” Bugbee, 1942 (Eremobates affinis)

1 Endemic subspecies (i.e., subspecies is found only in the White Sands dune field). 2 A different subspecies (S. u. tristichus) is dark at the Valley of Fires (Lewis, 1949). 3 A related species (P. intermedius ater) is dark at the Valley of Fires (Dice, 1929). 4 A related species (N. albigula melas) is dark at the Valley of Fires (Dice, 1929) Source Table 2: Probable mechanisms of color change for light-colored species at White Sands National Monument.

Goldman, 1933 Mechanism of color change Species Basis for conclusion Source Color fixed in Bleached earless lizard • Individuals held in lab on differ- Bundy, 1955 individuals (Holbrookia maculata ent-colored substrates do not Lowe & Norris, 1956 subspecies ruthveni) change color. Rosenblum, • Offspring from White Sands moth- in review ers are light in color when raised in Blair, 1941 Source the lab.

Cowles prairie lizard • Individuals held in lab with dif- Lowe & Norris, 1956 (Sceloporus undulatus ferent-colored substrates do not Rosenblum, Stroud, 1950 subspecies cowlesi) change color. in review • Offspring from White Sands moth- ers are light in color when raised in the lab.

Bugbee, 1942 Little striped Whiptail • Individuals held in lab with dif- Lowe & Norris, 1956 Stroud, 1950 (Aspidoscelis inornata ferent-colored substrates do not Rosenblum 2004 Stroud & Strohecker, 1949 formerly Cnemidophorus change color. inornatus) • A single gene (the Mc1r gene) is highly associated with light color- ation. Stroud, 1950 Apache pocket mouse • Dark individuals of the related P. Benson, 1933 (Perognathus flavescens intermedius ater from Valley of subspecies apachii) Fires held in lab with different- colored substrates do not change Stroud, 1950 color.

Camel cricket • Assertion by author. Stroud, 1950 (Ammobaenites phrixocnemoides Bugbee, 1942 subspecies arenicolus)

Camel cricket • Assertion by author. Stroud, 1950 (Daihinoides hastiferum subspecies larvale)

Bugbee, 1942 Color changes rapidly Spadefoot toad • Individuals in lab do change color. Stroud, 1949 to match substrate (Scaphiopus couchii)

Bugbee, 1942 Color changes at molt Locustid • Assertion by author. Stroud, 1950 to match substrate (Cibolacris parviceps subspecies arida)

Color derived from Lycosid spider • White color rubs off easily to re- Bugbee, 1942 environment veal brown underneath; color may still be internally derived. Literature Cited: brookia maculata and Sceloporus and the evolution of the Mc1r undulatus at White Sands gene. Evolution 58:1794-1808. Bagnara, J.T., and M.E. Hadley. National Monument, New Smith, H.M. 1943. The White 1973. Chromatophores and color Mexico. J. Herp. 35:326-330. Sands earless lizard. Zool. Ser. change: the comparative physiol Hager, S. B. 2001. Quantification of Field Mus. Nat. Hist. 24:339-344. ogy of animal pigmentation. body coloration for the lesser Smith, H.M. 1946. Handbook of Prentice Hall, Inc., NJ. earless lizard, Holbrookia macu Lizards: Lizards of the United Benson, S.B. 1933. Concealing col lata: Evidence for interpopula States and of Canada. Comstock oration among some desert tional differences. Southwest. Publishing Co., Ithaca, NY. rodents of the southwestern Nat. 47:229-307. Stroud, C.P. 1949. A white spade- United States. Univ. Calif. Pub. Kiltie, R. A. 1992. Tests of hypoth foot toad from the New Mexico Zool. 40:1-70. eses on predation as a factor White Sands. Copeia 1949:232. Blair, W.F. 1941. Annotated list maintaining polymorphic Stroud, C.P. 1950. A survey of the of mammals of the Tularosa melanism in coastal-plain fox insects of White Sands National Basin, New Mexico. Am. Midl. squirrels Sciurus niger L. Biol. J. Monument, Tularosa Basin, New Nat. 26:218-229. Linn. Soc. 451:17-38. Mexico. Am. Midl. Nat. 44:659- Blair, W.F. 1943. Ecological distri Lewis, T.H. 1949. Dark coloration 677. bution of mammals in the Tularo in the reptiles of the Tularosa Stroud, C.P., and H.F. Strohecker. sa Basin. Contrib. Lab. Vert. Biol., malpais, New Mexico. Copeia 1949. Notes on White Sands U. Mich. 20:1-24. 3:181-184. Gryllacrididae (Orthoptera). Bugbee, R.E. 1942. Notes on ani Lowe, C.H., and K. S. Norris. 1956. Proc. Ent. Soc. Wash. 51:125-126. mal occurrence and activity in A subspecies of the lizard Sce Zim, H.S., and H.M. Smith. 1987. the White Sands National Monu loporus undulatus from the Reptiles and Amphibians. Gold ment, New Mexico. Trans. Kans. White Sands of New Mexico. en Press, NY. Acad. Sci. 45:315-321. Herpetologica 12:125-127. Bundy, R.E. 1955. Color Variation Moritz, C.,1999. Conservation in Two Species of Lizards units and translocations: (Phrynosoma modestum and Strategies for conserving Holbrookia maculata subspecies) evolutionary processes. (Ph.D.): University of Wisconsin. Hereditas 130:217-228. Chapman, R.F. 1969. The Insects: Norris, K.S., and C.H. Lowe. 1964. Structure and Function. American An analysis of background Elsevier Publishing Co., Inc, NY. color-matching in amphibians Dice, L.R. 1929. Description of and reptiles. Ecology 45:565-580. two new pocket mice and a new Norris, K. S. 1965. Color adapta woodrat from New Mexico. tion in desert reptiles and its Occas. Papers Mus. Zool., U. thermal relationships. Lizard Mich. 203:1-4. Ecology: A Symposium. ed W.W. Dixon, J.R. 1967. Aspects of the Milstead. University of Missouri biology of the lizards of the Press, MI. White Sands, New Mexico. Rosenblum, E.B. in review. The role Contrib. Sci 129:1-22. of phenotypic plasticity in color Goldman, E.A. 1933. New variation of Tularosa Basin lizards. mammals from Arizona, New Rosenblum, E.B. in review. Mexico, and Colorado. J. Wash. Convergent evolution and Acad. Sci. 23:463-473. divergent selection: lizards at the Hager, S. B. 2000. Variation in body White Sands ecotone temperature and thermoregula Rosenblum, E.B. in prep. Ecologi tory behavior between two cal divergence and mating popultions of the lesser earless preference in the Lesser Earless lizard, Holbrookia maculata. Lizard. White Sands weevil Contemp. Herp. 2000:online. Rosenblum, E.B., H.E. Hoekstra, Hager, S. B. 2001. Microhabitat and M.W. Nachman. 2004. use and activity patterns of Hol Adaptive reptile color variation

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