Jemez Feral Guppies
McCauley Springs, New Mexico
© Alan S. Bias – February 17, 2017
Permission granted for nonprofit reproduction or duplication of photos and text in entirety with proper credit for learning purposes only.
All photos by author or by Tom Coggins with permission.
Nestled high in the Jemez Mountains of Sandoval County, New Mexico, at an elevation of around 7,350 feet (2240.28 meters) reside one of the most unique and oldest established feral populations of Poecilia reticulata in North America. This self-sustaining population of Guppies is not only a jewel for livebearer enthusiasts, but the focus of much formally published research.
As with most thermal spring environments throughout the United States, conditions can offer an oasis for a species evolved in tropical settings and unable to survive harsh seasonal weather fluctuations. Overall, size of habitable range is normally limited by temperature extremes, predation, and water chemistry to the first few pools near an issuing thermal source. In others habitation will extend downstream to a point where minimum survivable temperatures are no longer maintained during winter extremes.
While published research indicates a stocking date ca. 1975 or before of “feeder Guppies,” Jemez has varying sources suggesting initial dates of introduction ranging from the late 1940’s – 1960’s. This coincides with most North American feral populations. (Editor: The area has long drawn travelers to its warm springs; Guppy releases were likely intended to control mosquitos.)
Based on known genotype and phenotypical expressions, the Jemez population is unique in that individuals express little indication of founding members deriving from modern domestic Guppy strains. While likely not wild-caught, they show little in the way of domestication. Since their introduction having evolved into an interesting study population for researchers and breeders alike.
Prior published testing U.S. Geological Survey at McCauley Springs revealed a thermal discharge rate of between 310 – 400 gpm. The same study indicated an average discharge temperature of between 30.6 – 31.6ºC. Specific Conductance ranged between 160 – 180 S/cm.
Analysis of tritium levels at McCauley Springs were indicative of water entering the ground prior to 1953, though also suggestive of some water entering post this date. Water is circulated in the upper 1500’ of the ancient Valles Caldera moat and heated by geothermal heat flux common in the region. While many springs in the regions are much hotter, McCauley is generally considered a “Warm Spring,” with dilution in ground water supply, having a pH of 8.0 and corresponding lower levels of most minerals.
My Jemez study population derives from a large collection of individuals on July 15, 2016. Guppy habitation was limited primarily to the first two pools after thermal discharge. Greater numbers of Poecilia reticulata and Largespring Gambusia, Gambusia geserei, reside in the first pool, as compared to the second. Average depth of pools was around 3 feet at center with shallow edges. Water leaving the McCauley Spring Stream flows into the East Jemez River, before entering the Jemez River proper. Water temperature on the date of collection was just over 32.2ºC at spring source, with slightly varying pH readings of 8.0+. Water temperature in the first habitable pool was over 31.1*C, with a noticeable drop in the second pool. Each pool was strewn with sand and rock of varying size. An abundance of plant growth resembling Naja Grass (Najas guadalupensis) and algae was present in the first pool, while lower pools lacked vegetation.
The indicated pool temperature is considered within “habitable range” for Poecilia reticulata, though it is nearing the upper maximum limit. Extreme limit need not be “lethal” in immediate fashion to result in long-term repercussions. Male guppies have been demonstrated to have preference for slightly lower temperatures (24.5ºC) vs. females (28.2*C) for optimal development of secondary sexual characters; in the form of color ornaments and gonopodia. Lower temperatures can result in delayed maturation, and higher temperatures in deformity. Further studies support a reduction in overall body mass, growth, reproduction and locomotion, in both sexes, for individuals reared long-term in temperatures in excess of 30*C.
Just as temperature restricts these feral populations, so does predation. At McCauley predation in the first two pools is limited to resident non-native Gambusia geserei, birds, crustaceans, and insects. The presence of Common Mosquitofish, Gambusia affinis, in other locations is known to greatly restrict feral juvenile Guppy population levels. Native species of Rio Grande Sucker, Longnose Dace and Flathead Minnow are found in the East Fork of the Jemez River, well below the restricted Poecilia reticulata zone of habitation.
Collected fish showed no signs of parasitic infestation, nor have any appeared in subsequent captive-raised generations. This population may still retain genetic predisposition for resistance. Further benefit is derived in the form of constant high water temperature beyond 28.9ºC, which is lethal to Ichthyobodo necator (Costia). Individuals pretty much match descriptions of published research by Nicoletto & Kodric-Brown (See: Scientific Study Excerpts). Overall individuals are very reflective with minimal ornamental orange spotting in those collected, and F1 offspring.
Captive bred F2 and F3 show an expected increase in both red and yellow color ornaments in males, when reared with no predation. Spotting remains very distinct, with circular patches surrounded by iridophore / leucophores circular rings. Also, noted is an increase in upper and lower sword ornaments with minimal extension.
Nearly all collected males and offspring are hyaline dorsal. Some express black melanophores in the dorsal, but not the trait described by geneticist Øjvind Winge as maculatus. The majority of males express basic wild-type oval-tail, a percentage small top-sword with minimal extension, and the remainder rudimentary flag-tails. A very reflective iridophore ring surrounds primary ectopic melanophore “eye spots” in the anterior body. Violet-blue iridophore pattern is present, in nearly all males in the body, to include long linear patches.
Potential extreme temperature issues manifest in two forms in collected individuals: size and shape. Size reduction is evident both sexes collected at McCauley Springs. However, this condition did not completely manifest in F1 offspring reared under cooler temperatures. Males and females showed dramatic increase in size under optimum temperature and feeding regimen. Though size disparity remained between the sexes, with females expressing a proportionally larger increase in overall size.
A high percentage of collected females expressed little or no tapering of posterior peduncle, likely as a result of high environmental temperatures in the first pool. This “thickness” has alleviated somewhat in captive raised fish, though in general thickness in female body form is much greater than many wild or captive bred populations. Males in turn, have demonstrated just the opposite. Collected males demonstrate a “linear and lanky” appearance, despite low velocity water conditions. Captive reared, to a high degree, are much more robust in body type. In general, the overall body size has increased and lengthened in both males and females.
All fish appear to be heterozygous or homozygous Purple Body Mutation (Pb). Lifespan appears longer than some feral populations I have worked with, and consistent with others. Research indicates they have evolved over multiple generations under limited predation on a diet consisting mostly of algae. Jemez males phenotypically resemble the Kemp 2008 Quare study population in many ways, and likely demonstrate the same fairly low UV peaks. Melanophore ornaments are both circular and linear, with the latter more predominant. Good fertility is evident, with moderate size litters of 15-30 fry. Based on breeding results this population shows little, if any, sign of additional infusion from other sources since initial stocking(s). All research papers seem hesitant to cite stocking date earlier than late 1960-70’s. From what I have informally gathered and observed, it seems likely an earlier stocking date is more than plausible.
A percentage of males express Iridescens (Ir); “reflective dorsal spot”. This in itself is suggestive of a much earlier stocking date. Ir was present in early breeder tanks 1920-40’s and prior to modern collections of Poecilia reticulata wingei (to include those known as Endler’s Livebearer).
All females are color tail / neutral oval-tail, with the exception of limited purple-blue iridophores (Pb expression) &/or yellow xanthophore in the form of Flavis (Fla) in the caudal base. Females express much in the way of reflective qualities, as found in males, as compared to many other feral populations or wild populations. Including purple-blue iridophores, heavy reticulation, and black striping on anterior shoulders along the lateral line. This is suggestive of “overall” Jemez reflectivity stemming from X-link &/or autosomal modes of inheritance. Population appears homozygous grey, in wild caught and in captive bred to date.
Surprisingly, this population does not exhibit a very high “fright or flight” response to human traffic or movement from above, and is known for gathering in large schools around bathers entering the pools. Under high temperature parameters this increased mobility may be indicative of low predation levels on adults (Gambusia geserei predation limited to juveniles) &/or low satiation levels (limited food resources in small area of habitation) for the group constituents as a whole. Collected individuals easily settle into captivity in uncovered tanks with high water levels. Readily respond to feeding, and unlike Poecilia reticulata wingei variants, take little notice during tank maintenance. Though interestingly, when removed and confined to small tanks during photography, males expressing near wild-type color ornaments exhibit higher levels of agitation and continuous movement, as opposed to those expressing increased color/pattern arising from lack of predation in captive rearing.
RESEARCH STUDY EXCERPTS
Kodric-Brown (1989) utilized 2 study populations, Paria wild [Trinidadian] and Jemez feral [McCauley Springs, NM]. McCauley Springs feral express reduced orange spotting in comparison to other populations. Not surprisingly, it was reported “Females from the Jemez population showed significant disagreement in their preferences for individual males.” Jemez males exhibit increased iridophore spotting (blue and white), and increased circular and linear melanophore spots. Jemez males are very iridescent purple-blue, often expressing: Iridescens (Ir), (Winge 1922b; See also: Iridscens (Ir), Blacher 1928; Smargd Iridescens (SmIr), Dzwillo 1959; Blue Iridescent Spot, Kottler 2013; Reflective Dorsal Spot (RDS), Bias 2013).
The wild type guppies used in this study were from a third generation laboratory colony derived from a feral population located in the McCauley hot spring in the Jemez Mountains of New Mexico. This population has been there for at least 16 years (R. Thorn-hill, personal communication). All fish appeared to be in good physical condition. The three male tail types used were upper sword, flag, and round… …These three tail types are common in the McCauley springs population (personal observation). (Nicoletto 1991).
Offspring reared in the laboratory encountered different environmental conditions from their field-caught sires. A laboratory environment, with its abundant food and constant conditions, may have permitted the expression of ornaments in male offspring that were present, but not expressed, in field-caught sires… …In other words, in the laboratory environment we may find an uncoupling of ornamentation and constitution, so differences in the ornamentation of offspring of different sire types were not observed. The uncoupling argument may also explain why the offspring of preferred males were not more ornamented than the offspring of non-preferred males as both the Fisherian and adaptive models predict. (Nicoletto 1995)
In this study, the field-caught sires had significantly fewer orange spots with less relative area than their laboratory reared sons… …and the heritability estimate for orange was not significantly different from zero, indicating little or no heritability. This suggests that the sires may have been unable to express their orange ornamentation because of adverse environmental conditions. The environment of the Jemez Mountain sires is highly oligotrophic and the fish feed primarily on algae. I examined the gut contents of 27 guppies in 1987 from the Jemez population and found all to contain algae, and only one large female contained a single unidentified insect. Although nothing is known about the development of orange ornamentation in guppies reared exclusively on a diet of algae, they are known to have slower growth rates than guppies fed Daphnia or Tetramin (Dussault & Kramer 1981). (Nicoletto 1995)
Guppies used in this study were the laboratory-born offspring of field-caught guppies from a feral population located in McCauley Hot Spring in the Jemez Mountains of New Mexico. This population has lived in the spring for at least 23 years (Koster W, personal communication). These fish are descendants of domesticated “feeder guppies” that are somewhat similar in appearance to wild-type guppies (Nicoletto, 1993), but they are probably not as variable (Endler JA, personal communication). (Nicoletto 1996)
Jemez males had significantly more iridescent coloration (x = 29.6%, SE= 11.40) than Trinidad males (x = 4.380, SE = 4.45). Jemez males also had two types of iridescent spots, blue and white, whereas Trinidad males only had white spots. There were no significant differences between Trinidad and Jemez males for the percent of their bodies covered with orange or black color spots… Both Trinidad and Jemez females preferred males with high display rates, but differed in the relative visually-preferred males. (Kodric-Brown 1996)
Jemez females preferred males with larger areas of carotenoid spots, and pattern complex-ity. Female choice of males with complex color patterns may, in part, explain the high degree of disagreement among the Jemez females in their choices of males. However, complexity of the color pattern did not seem to be an important factor in the PCA analy-sis. (Kodric-Brown 1996)
Guppies used in these experiments were descendants from a feral population in McCauley Hot Spring in the Jemez Mountains of New Mexico. This population has lived in the spring for at least 24 years. These fish are descendants of ‘feeder guppies’ that are similar in appearance to wild-type guppies, although they may be more variable in their mate preferences (Nicoletto 1993, Kodric-Brown & Nicoletto 1996). Mating preferences of this population have been extensively studied. Females differentially respond to males with high display rates (Nicoletto 1993) and to displays of longer duration (Nicoletto 1996). Jemez females also respond preferentially to males with more complex ornamentation and more orange color on their body (Nicoletto 1993). However, courtship vigor is correlated with carotenoid pigmentation, and when the variance in display rate is statistically controlled the preference for males with more orange color disappears. In this respect Jemez guppies differ from other guppy populations (Endler 1980, 1983, Endler & Houde 1995, Houde 1987, 1988, Kodric-Brown 1985, 1989). (Nicoletto & Kodric-Brown 1999)
Jemez males also have extensive iridescent ornamentation. The role of these iridescent colors in mate choice is unknown. They may function in long-distance attraction of females (Endler 1983). In this study females did not respond to differences in the blue treatment, and this is consistent with some previous studies using live males (Nicoletto 1993, 1995). However, in a study of mate preferences by Kodric-Brown & Nicoletto (1996) a Principal Component analysis showed that some females in this population preferentially responded to males with extensive iridescent ornamentation. Iridescent blue and/or violet coloration also seems to be an important criterion in mate choice of several populations of Trinidadian guppies (Endler & Houde 1995). (Nicoletto & Kodric-Brown 1999)
Fish used in our experiments were laboratory-reared, first generation descendants of females caught at McCauley Spring in the Jemez Mountains near Albuquerque, New Mexico. The population was established by introduction approximately 30 yrs previously. It experiences low predation pressure, since there are no piscivorous fish. Males are highly ornamented, with large areas of the body and fins covered with red and yellow (carotenoid), black (melanin), and iridescent (mostly blue and white) spots. Females prefer males with complex color patterns, large areas of carotenoid pigment, and high display rates (Nicoletto 1993, 1995). (Kodric-Brown 2001)
Jemez females mature much later than females from Trinidadian populations that experience low predation and high adult survivorship. Typically, less than half of the Jemez females mated to males at 3–4 months old produced broods, whereas females from Trinidad were fully sexually mature at that age (Reznick et al. 1996). We chose 6-mo-old females because at that age all are mature and can produce a brood. At 12 mo, all Jemez females are still reproductively active. In the laboratory, Jemez females senesce and begin to die at an age of 18–24 mo. Senescence is characterized by smaller brood size or cessation of reproduction. Although we have no information about the age of females in Jemez Springs, gravid females of the size class of our laboratory-reared 12-mo-old females are quite numerous. (Kodric-Brown 2001)
Age had a significant effect on female responsiveness to the showy male image. Six-month-old virgin females spent significantly more time viewing the image of the showy male than 12-mo-old virgin females. A greater number of females preferred the showy male at the age of 6 mo[nths] than at 12 mo[nths] or after mating and producing a brood… Thus, female preference for showy males decreased with age. Mating experience had no effect on the responses of females to showy males. Twelve-month-old virgin females and postpartum females spent approximately equal amounts of time viewing both showy and plain males. (Kodric-Brown 2001)
Our results document changes in female responsiveness based on one criterion, male ornamentation, specifically the area of carotenoid spots. The intensity and size of carotenoid spots are important criteria for female choice in all populations of guppies examined to date, including laboratory stocks (e.g., Farr 1980; Kodric-Brown 1993), naturalized populations (e.g., Nicoletto 1993; Brooks and Caithness 1995), and native populations in Trinidad (e.g., Endler and Houde 1995). However, our results should not be taken to imply that older females are incapable of discriminating among males and do not show preferences for particular male traits. Because we tested only the area of carotenoid spots, we cannot rule out mate choice based on other criteria, such as other pigment patterns or courtship displays. Females from the Jemez population do show strong preferences for vigorously displaying males (Nicoletto 1993, 1995). So older females may well select males based primarily on the vigor and duration of courtship displays rather than carotenoid pigments… Our results have important implications for studies of sexual selection. They suggest that criteria for mate choice may change with female age, thus altering selection for multiple male secondary sexual traits, including male courtship tactics. If older females are less responsive to male morphological traits, such as carotenoid color spots, then males might compensate in their courtship tactics and engage in more vigorous displays. Indeed, male guppies have been reported to increase their courtship displays toward larger, and presumably older, females (Baerends et al. 1955; Houde 1997). (Kodric-Brown 2001)
When females were presented with ‘mixed signals,’ namely dull males courting intensely, and males with orange coloration and low levels of courtship, there was no significant difference in the time they spent with each image, because females varied in their preferences for each image. These results are consistent with the interpretation that the dynamic (courtship display) and the static signals (orange color) are equally attractive. Our results also support an alternative interpretation, namely that females of this population show individual preferences in the relative ranking of these two traits: some may show a preference for orange color, while others may base their preference on display rate. The observed patterns are also consistent with those found in a previous study of Jemez guppies using live males, where females differed in their preferences for male ornaments (carotenoid and iridescent spots (Kodric-Brown and Nicoletto 1996). (Kodric-Brown 2001)
To determine whether predation pressure affects female preference for males with UV-reflective colour patterns, we compared the responses of Jemez females with those of Quare females. The Jemez females were from a population of naturalized guppies in McCauley spring located in the Jemez Mountains of New Mexico, U.S.A. The Jemez population was introduced into the spring over 30 years ago, and since then has had no piscivorous predators. (Kodric-Brown 2001)
Male UV Reflectance Patterns Colour patterns of Jemez males showed UV-reflective components that covered 4–31% of the body area. Most, but not all, of the iridescent colours also reflected below 400 nm (near UV and UV). Among the iridescent colours, white and purple strongly reflected below 400 nm, but green and blue did not. Gold (yellow–orange) also showed a UV component. Generally, the area of UV reflectance closely matched the area of iridescence visible in longer wavelengths. Although the overall colour pattern was the same when viewed in the visible and the short wavelengths, certain aspects of the pattern were more noticeable in the UV wavelengths. Melanin (black) spots surrounded, either completely or partially, by a ring of iridescent white, and gold spots next to black areas provided a striking contrast in the UV. (Kodric-Brown 2001
Jemez females Responses to male pairs matched for all colours. Females spent almost twice as long observing a male behind the UVT partition as they did the same male viewed behind the UVB partition. These results suggest that females not only respond to the UV-reflective components of the male colour patterns, but that these components contribute to the overall attractiveness of a male. Responses to male pairs differing in UV reflectance area. Females, when given a choice between pairs of males that were matched for carotenoids and iridescence but differed in UV reflectance, consistently chose the male of the pair behind the UVT partition. Difference in the time females spent with the more ornamented male of the pair was positively correlated with the difference in the area of UV reflectance between the pairs. These results indicate that females respond to the area of a male’s colour pattern that reflects UV wavelengths. Responses to male pairs differing in carotenoid area. There was no effect of treatment (UVT versus UVB) on female responses to male pairs that differed in the area of carotenoids but were matched for area of iridescence and UV reflectance. Similarly, there was no positive correlation between the time females spent with the more ornamented male of the pair when he was behind the UVT partition. Jemez females Responses to the UV-reflective components of male colour patterns. Females from both populations spent longer viewing males when the males were placed behind the UVT partition than when the same males were placed behind the UVB partition. Jemez and Quare females responded in a similar way to manipulations of the UV-reflective component of male colour patterns. Predation level thus does not seem to affect female responses to UV-reflective components of male colour patterns. (Kodric-Brown 2001).
Jemez Feral Guppies continue to offer researchers an ongoing opportunity to study an evolving population within the confines of North America. They also offer breeders a unique set of “genetic tools” for use in domestic breeding programs.
My initial test outcrosses are only in early stages. Yet, based on observations of my half-dozen feral breeding colonies a host of potential benefits are possible in outcross offspring for color, pattern and reflection. It is rare for breeders to identify a breeding population or strain of Poecilia reticulata with the reflective qualities and pattern expression exhibited in Jemez, outside of selectively bred Swordtail strains or from infusions of P. reticulata wingei variants. While published research as quantified Jemez ornamental traits along scientific standards, little has been documented along breeder recognized traits and mode of inheritance.
Many thanks to my friend, and fellow collector / breeder Tom Coggins (Missouri) for this recent collection. Tom went out of his way to not only make this collection in New Mexico, but deliver them in entirety two weeks later at my Southern WV home.
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