Wild Tiger Research Articles

Genetic diversity of intensive cultured and wild tiger shrimp Penaeus monodon (Fabricius) in Malaysia using microsatellite markers

Inbreeding as negative factor perhaps promote a significant increase of the genetic similarity of the captive populations, consequently leading to greater disease susceptibility and impairment of both the growth and final size of the shrimps. Therefore evaluating genetic diversity and inbreeding required for improvement of brood stock management will assist shrimp breeders to minimize or avoid inbreeding coefficient. The objective of this study was to assess the genetic diversity of intensive cultured and wild tiger shrimp Penaeus monodon (Fabricius) in Malaysia using six microsatellite markers (CSCUPmo1, CSCUPmo2, CSCUPmo3, CSCUPmo4, CSCUPmo6 and CSCUPmo7). The mean numbers of allele, observed heterozygosis, and polymorphism information content (PIC) index were calculated. The observed allele’s sizes at the investigated loci were similar to those of previous reports. The number of alleles yielded by all microsatellites ranged from 2 to 6 alleles. The highest and the lowest effective number of alleles were found in CSCUPmo1 (4.16) and CSCUPmo7 (1.3), respectively. The most frequent alleles (MFA) for CSCUPmo1, CSCUPmo2, CSCUPmo3, CSCUPmo4, CSCUPmo6 and CSCUPmo7 bp were 259, 165, 181, 242, 206 and 218 bp, respectively. Brood stock showed lower genetic diversity value than wild population. However, with an observed heterozygosity (H obs ) below expectations it would be necessary to introduce cross breeding among hatcheries to reduce the risk of inbreeding depression. Microsatellite markers analysis was able to characterize the genetic divergence between the brood stocks and wild population and could be helpful tools for defining better management strategies of these P. monodon (Fabricius) in Malaysia. Keywords: Inbreeding, Penaeus monodon (Fabricius), Malaysia, microsatellite markers.

Population of bottleneck and microsatellite: An Analysis Based on genetic diversity of Wild Tiger Shrimp Penaeus monodon (Fabricius) in Malaysia

In the present study, six microsatellite markers, namely, CSCUPmo1, CSCUPmo2, CSCUPmo3, CSCUPmo4, CSCUPmo6 and CSCUPmo7 were used to monitor genetic variation in the wild tiger shrimp, Penaeus monodon (Fabricius). The number of alleles examined by all the microsatellites yielded the monitoring ranges of 2 to 6 alleles. Moreover, the highest and lowest heterozygosity were found to be at a significant level of 0.33 in CSCUPmo1 and at a significant level of 0.47 in CSCUPmo2, respectively. These observations indicated the existence of substantial genetic diversity in P. monodon in Malaysia. None normal 'L' shaped distribution of mode-shift test, significant heterozygote excess on the basis of different models, as revealed from Sign, standardized differences and Wilcoxon sign rank tests as well as significant M ratio value suggested that there was recent bottleneck in the existing population, providing important information for shrimp breeders. Key words : Genetic bottleneck, Penaeus monodon, microsatellite, heterozygote.

Genetic diversity of intensive cultured and wild tiger shrimp Penaeus monodon (Fabricius) in Malaysia using microsatellite markers

Inbreeding as negative factor perhaps promote a significant increase of the genetic similarity of the captive populations, consequently leading to greater disease susceptibility and impairment of both the growth and final size of the shrimps. Therefore evaluating genetic diversity and inbreeding required for improvement of brood stock management will assist shrimp breeders to minimize or avoid inbreeding coefficient. The objective of this study was to assess the genetic diversity of intensive cultured and wild tiger shrimp Penaeus monodon (Fabricius) in Malaysia using six microsatellite markers (CSCUPmo1, CSCUPmo2, CSCUPmo3, CSCUPmo4, CSCUPmo6 and CSCUPmo7). The mean numbers of allele, observed heterozygosis, and polymorphism information content (PIC) index were calculated. The observed allele’s sizes at the investigated loci were similar to those of previous reports. The number of alleles yielded by all microsatellites ranged from 2 to 6 alleles. The highest and the lowest effective number of alleles were found in CSCUPmo1 (4.16) and CSCUPmo7 (1.3), respectively. The most frequent alleles (MFA) for CSCUPmo1, CSCUPmo2, CSCUPmo3, CSCUPmo4, CSCUPmo6 and CSCUPmo7 bp were 259, 165, 181, 242, 206 and 218 bp, respectively. Brood stock showed lower genetic diversity value than wild population. However, with an observed heterozygosity (H obs ) below expectations it would be necessary to introduce cross breeding among hatcheries to reduce the risk of inbreeding depression. Microsatellite markers analysis was able to characterize the genetic divergence between the brood stocks and wild population and could be helpful tools for defining better management strategies of these P. monodon (Fabricius) in Malaysia. Keywords: Inbreeding, Penaeus monodon (Fabricius), Malaysia, microsatellite markers.

Population Status of a Cryptic Top Predator: An Island-Wide Assessment of Tigers in Sumatran Rainforests

Large carnivores living in tropical rainforests are under immense pressure from the rapid conversion of their habitat. In response, millions of dollars are spent on conserving these species. However, the cost-effectiveness of such investments is poorly understood and this is largely because the requisite population estimates are difficult to achieve at appropriate spatial scales for these secretive species. Here, we apply a robust detection/non-detection sampling technique to produce the first reliable population metric (occupancy) for a critically endangered large carnivore; the Sumatran tiger (Panthera tigris sumatrae). From 2007–2009, seven landscapes were surveyed through 13,511 km of transects in 394 grid cells (17×17 km). Tiger sign was detected in 206 cells, producing a naive estimate of 0.52. However, after controlling for an unequal detection probability (where p = 0.13±0.017; ±S.E.), the estimated tiger occupancy was 0.72±0.048. Whilst the Sumatra-wide survey results gives cause for optimism, a significant negative correlation between occupancy and recent deforestation was found. For example, the Northern Riau landscape had an average deforestation rate of 9.8%/yr and by far the lowest occupancy (0.33±0.055). Our results highlight the key tiger areas in need of protection and have led to one area (Leuser-Ulu Masen) being upgraded as a ‘global priority’ for wild tiger conservation. However, Sumatra has one of the highest global deforestation rates and the two largest tiger landscapes identified in this study will become highly fragmented if their respective proposed roads networks are approved. Thus, it is vital that the Indonesian government tackles these threats, e.g. through improved land-use planning, if it is to succeed in meeting its ambitious National Tiger Recovery Plan targets of doubling the number of Sumatran tigers by 2022.

A landscape-based conservation strategy to double the wild tiger population

In an unprecedented response to the rapid decline in wild tiger populations, the Heads of Government of the 13 tiger range countries endorsed the St. Petersburg Declaration in November 2010, pledging to double the wild tiger population. We conducted a landscape analysis of tiger habitat to determine if a recovery of such magnitude is possible. The reserves in 20 priority tiger landscapes can potentially support >10,000 tigers, almost thrice the current estimate. However, most core reserves where tigers breed are small and land-use change in rapidly developing Asia threatens to increase reserve and population isolation. Maintaining population viability and resilience will depend upon a landscape approach to manage tigers as metapopulations. Thus, both site-level protection and landscape-scale interventions to secure habitat corridors are simultaneous imperatives. Co-benefits, such as payment schemes for carbon and other ecosystem services, should be employed as strategies to mainstream landscape conservation in tiger habitat into development processes.

The Once and Future Tiger

In reeds tinged red by the Central Asian sun, a tiger once roamed. There, in riparian forests that line rivers like the Vakhsh on the border of the former Soviet country Tajikistan, the Caspian tiger (Panthera tigris virgata) prowled. Until its extinction in the mid1900s, the tiger stalked Bukhara deer along tugai, thicketed watercourses that flow through Central Asia’s otherwise vast, arid deserts. The tiger’s route took it across shaded rivers and onto muddy banks. Peering into shoreline bracken, the tiger crawled through a latticework of tangled low shrubs, finally emerging into the willow and poplar forests favored by its deer prey. And into trouble. In the early 20th century, the Russian government instructed its army to exterminate all tigers as part of an agricultural conversion project across Central Asia. Once Caspian tigers were almost gone, farmers moved in, clearing tugai and planting crops such as cotton. The tigers retreated, first from lowland streams to marshes around larger rivers. Finally, they crept into forested mountain ranges. The Caspian tiger’s last stronghold was a reserve in Tajikistan: Tigrovaya Balka, “tiger former river channel.” The name was given to this first of Central Asia’s protected areas, or In 1947, Russia banned hunting of the Caspian tiger’s close relative, the Siberian, or more properly Amur, tiger (Panthera tigris altaica), still found today near the Amur River in the Russian Far East. But the edict came too late for the Caspian tiger, says Carlos Driscoll, a biologist at the US National Cancer Institute’s Laboratory of Genomic Diversity in Frederick, Maryland. The last tiger in Tigrovaya Balka was glimpsed in 1958. Although still a matter of debate, the legendary final wild Caspian tiger may have been killed in February 1970, in Hakkari Province, Turkey. New DNA evidence, however, reveals that we may not have seen the last of this tugai tiger.

China’s Captive Tigers: An Application of the Precautionary Principle to Policy

Tigers have been subject to large and prolonged declines in the wild for several reasons, including poaching. Policies to arrest this decline have been ongoing but marked by failure. One controversial element of the management of tigers is the large captive-breeding facilities in China. This controversy stems from uncertainties about the consequences of these facilities and the best policies to pursue. These uncertainties motivate the employment of the precautionary principle in this research. The precautionary principle is appropriate given the high levels of uncertainty associated with tiger conservation. The precautionary principle is intended to avoid irreversible biodiversity losses. This means the primary concern is the likelihood of different strategies leading to a decline in wild tiger numbers rather than the potential for an increase. This paper applies the precautionary principle to three policy options. These options are to; first, close the facilities down; second, continuing to maintain a large captive population; and third, to resume It is argued that the precautionary principle favours maintaining a high captive population to forestall a consumer switch to black-market sources. Given that this situation is not sustainable, research to resolve some important information gaps is imperative.

Bringing the Tiger Back from the Brink—The Six Percent Solution

The Tiger Summit, to be hosted by Prime Minister Vladimir Putin in Russia in November 2010—the Chinese Year of the Tiger and the International Year of Biodiversity—promises to be the most significant meeting ever held to discuss the fate of a single non-human species. The Summit will culminate efforts by the Global Tiger Initiative (GTI), launched in 2008 by Robert Zoellick, World Bank President. Leaders of 13 tiger range states, supported by international donors and conservationists attending the summit, are being asked to commit to substantive measures to prevent the unthinkable: extinction of the world's last wild tiger populations. Wild tiger numbers are at an historic low. There is no evidence of breeding populations of tigers in Cambodia, China, Vietnam, and DPR Korea. Current approaches to tiger conservation are not slowing the decline in tiger numbers [1]–[3], which has continued unabated over the last two decades. While the scale of the challenge is enormous, we submit that the complexity of effective implementation is not: commitments should shift to focus on protecting tigers at spatially well-defined priority sites, supported by proven best practices of law enforcement, wildlife management, and scientific monitoring. Conflict with local people needs to be mitigated. We argue that such a shift in emphasis would reverse the decline of wild tigers and do so in a rapid and cost-efficient manner.

Habitat evaluation of wild Amur tiger ( Panthera tigris altaica) and conservation priority setting in north-eastern China

The Amur Tiger ( Panthera tigris altaica) is one of the world’s most endangered species. Recently, habitat fragmentation, food scarcity and human hunting have drastically reduced the population size and distribution areas of Amur tigers in the wild, leaving them on the verge of extinction. Presently, they are only found in the north-eastern part of China. In this study, we developed a reference framework using methods and technologies of analytic hierarchy process (AHP), remote sensing (RS), geographic information system (GIS), GAP analysis and Natural Break (Jenks) classification to evaluate the habitat and to set the conservation priorities for Amur tigers in eastern areas of Heilongjiang and Jilin Provinces of northeast China. We proposed a Habitat Suitability Index (HSI) incorporating 7 factors covering natural conditions and human disturbance. Based on the HSI values, the suitability was classified into five levels from the most to not suitable. Finally, according to results of GAP analysis, we identified six conservation priorities and designed a conservation landscape incorporating four new nature reserves, enlarging two existing ones, and creating four linkages for Amur tigers in northeast China. The case study showed that the core habitats (the most suitable and highly suitable habitats) identified for Amur tigers covered 35,547 km 2, accounting for approximately 26.71% of the total study area (1,33,093 km 2). However, existing nature reserves protected only (7124 km 2 or) 20.04% of the identified core habitats. Thus, enlargement of current reserves is necessary and urgent for the tiger’s conservation and restoration. Moreover, the establishment of wildlife corridors linking core habitats will provide an efficient reserve network for tiger conservation to maintain the evolutionary potential of Amur tigers facing environmental changes.

Prevalence of shrimp viruses in wild Penaeus monodon from Brunei Darussalam

Over a period of 30 months, wild black tiger shrimp ( Penaeus monodon) were collected from the South China Sea in South-east Asia, in an effort to establish specific pathogen free (SPF) stocks of P. monodon in Brunei Darussalam. The viral status of the broodstock was assessed by real-time and conventional polymerase chain reaction (PCR) using DNA and reverse transcribed RNA extracted from the gill, hepatopancreas and pleopods. Histopathology was performed to confirm PCR results. Over 270 P. monodon were collected, screened and spawned. Of the nine viruses assessed, infectious hypodermal and hematopoietic necrosis virus (IHHNV) was most commonly detected (19.6%), followed by monodon baculovirus (MBV) (7.4%), hepatopancreatic parvovirus (HPV) (3.8%), and Mourilyan virus (MoV) (0.9%). The only multiple viral infections found were a combination of IHHNV and MBV (2.2%). Interestingly, the two most virulent viruses for P. monodon, white spot syndrome virus (WSSV) and yellowhead virus (YHV) were not detected in any shrimp. It is concluded that wild P. monodon from Brunei waters have a low prevalence of viral pathogens, which has permitted the development of SPF stocks as a foundation population for selective breeding.

Forests of the Night: Refugia of Genetic Diversity in Wild Tigers

Having amassed non-invasively collected samples from 73 tigers from 28 Indian reserves, Mondol, Karanth, and Ramakrishnan have published a comprehensive study of genetic variation in tigers in PLoS Genetics [1]. Incorporating information on mitochondrial haplotypes and microsatellite allelic diversity from previous studies, their additional data from the wild tiger populations in India demonstrate that the greatest extent of tiger genetic diversity resides in the Indian subcontinent. The expansion and refinement of knowledge pertaining to tiger phylogeography and population genetics comes at a time when small population vulnerabilities, poaching, and habitat loss conspire to produce an apocalypse for these charismatic cats.

Why the Indian Subcontinent Holds the Key to Global Tiger Recovery

With only ∼3,000 wild individuals surviving restricted to just 7% of their historical range, tigers are now a globally threatened species. Therefore, conservation efforts must prioritize regions that harbor more tigers, as well try to capture most of the remaining genetic variation and habitat diversity. Only such prioritization based on demographic, genetic, and ecological considerations can ensure species recovery and retention of evolutionary flexibility in the face of ongoing global changes. Although scientific understanding of ecological and demographic aspects of extant wild tiger populations has improved recently, little is known about their genetic composition and variability. We sampled 73 individual tigers from 28 reserves spread across a diversity of habitats in the Indian subcontinent to obtain 1,263 bp of mitochondrial DNA and 10 microsatellite loci. Our analyses reveals that Indian tigers retain more than half of the extant genetic diversity in the species. Coalescent simulations attribute this high genetic diversity to a historically large population size of about 58,200 tigers for peninsular India south of the Gangetic plains. Furthermore, our analyses indicate a precipitous, possibly human-induced population crash ∼200 years ago in India, which is in concordance with historical records. Our results suggest that only 1.7% (with an upper limit of 13% and a lower limit of 0.2%) of tiger numbers in historical times remain now. In the global conservation context our results suggest that, based on genetic, demographic, and ecological considerations, the Indian subcontinent holds the key to global survival and recovery of wild tigers.

Condition‐dependent mate choice and a reproductive disadvantage for MHC‐divergent male tiger salamanders

Major histocompatibility complex (MHC) alleles likely have adaptive value because of overdominance, in which case MHC heterozygous individuals have increased fitness relative to homozygotes. Because of this potential benefit, the evolution of sexual reproduction between MHC-divergent individuals (i.e. negative assortative mating, NAM) may be favoured. However, the strongest evidence for MHC-based NAM comes from inbred animals, and context-dependent mating preferences have rarely been evaluated although they often occur in nature. We assessed the extent MHC-based mating preferences among wild tiger salamanders (Ambystoma tigrinum) using multiple molecular approaches. We genotyped 102 adults and 864 larvae from 36 breeding trials at both microsatellite and MHC loci. Parentage analysis revealed that reproductive success among males was positively associated with increased tail length and that with respect to the focal female, MHC-similar males sired a significantly higher number of offspring than more dissimilar males. This trend was consistent, even under context-dependent scenarios that favour traditional MHC-based NAM. These results suggest that the most MHC-divergent males may be at a reproductive disadvantage in pairwise breeding trials. Our data add to a growing body of evidence that suggests where it exists, MHC-based choice is probably dynamic and mediated by many factors that vary in the wild, notably signals from other indicator traits and by the quality and quantity of potential mates.

In situpopulation structure andex siturepresentation of the endangered Amur tiger

The Amur tiger (Panthera tigris altaica) is a critically endangered felid that suffered a severe demographic contraction in the 1940s. In this study, we sampled 95 individuals collected throughout their native range to investigate questions relative to population genetic structure and demographic history. Additionally, we sampled targeted individuals from the North American ex situ population to assess the genetic representation found in captivity. Population genetic and Bayesian structure analyses clearly identified two populations separated by a development corridor in Russia. Despite their well-documented 20th century decline, we failed to find evidence of a recent population bottleneck, although genetic signatures of a historical contraction were detected. This disparity in signal may be due to several reasons, including historical paucity in population genetic variation associated with postglacial colonization and potential gene flow from a now extirpated Chinese population. Despite conflicting signatures of a bottleneck, our estimates of effective population size (N(e) = 27-35) and N(e)/N ratio (0.07-0.054) were substantially lower than the only other values reported for a wild tiger population. Lastly, the extent and distribution of genetic variation in captive and wild populations were similar, yet gene variants persisted ex situ that were lost in situ. Overall, our results indicate the need to secure ecological connectivity between the two Russian populations to minimize loss of genetic diversity and overall susceptibility to stochastic events, and support a previous study suggesting that the captive population may be a reservoir of gene variants lost in situ.

Polymorphism of Alternative Splicing of Major Histocompatibility Complex Transcripts in Wild Tiger Salamanders

Polymorphism of Alternative Splicing of Major Histocompatibility Complex Transcripts in Wild Tiger Salamanders

The Black Market in China for Tiger Products

China is an important source of demand for tiger products. Given most wild tiger populations are found in neighboring Asian states, criminal organizations have developed to procure, transport and distribute tiger products. Their organizational form adjusts to reduce the most significant transaction cost faced at each stage in the supply chain. Procurement is subcontracted to skilled local hunters. Tiger forms a minority part of a wider portfolio of wildlife harvested by poachers. Transport to the Chinese border is the largest cost and minimized by use scale economies to transport wildlife products in bulk. Successful criminal organizations have evaded detection for years. In China Tibet absorbs of the demand for skin, while bone is consumed as medicine in Eastern provinces. There is not an homogeneous black market in tiger parts in China. Harsh penalties in China for tiger trafficking favor networks that specialize in the distribution of just tiger bone, with few intermediaries and likely in secretive settings. Transaction costs limit the penetration of tiger parts to provinces that are proximate to range states. The ability of law enforcement agencies to reduce poaching to safe levels appears unlikely given the evasions strategies available to smugglers.

Prevalence of monodon baculovirus (MBV) in wild shrimp Penaeus monodon in the Philippines

Prevalence of monodon baculovirus (MBV) was determined using polymerase chain reaction (PCR) on deoxyribonucleic acid (DNA) extracts from the hepatopancreas of the wild black tiger shrimp, Penaeus monodon collected from 7 sampling sites in the Philippines. These sites are considered as the primary sources of broodstock and spawners used for hatchery operations. MBV was detected from all sites except Palawan during the dry season and Negros Occidental and Bohol during wet season. The prevalence of MBV showed no seasonal, sex and size variations. These results show that MBV is an established viral infection in wild populations of Penaeus monodon in the Philippines. Broodstock collected from the contaminated sites could serve as a reservoir of the virus which could infect the post-larvae used to stock in grow-out ponds.

Shifts in genetic diversity during domestication of Black Tiger shrimp, Penaeus monodon, monitored using two multiplexed microsatellite systems

Differences in genetic diversity between wild and domesticated Black Tiger shrimp ( Penaeus monodon) were assessed in five stocks using molecular markers. These stocks represent an Australian wild population from a single location, and four populations of domesticated animals originating from the same location. Two established high-throughput genotyping systems with a total of 12 microsatellite markers were used to assess diversity of farmed stocks in comparison to wild-caught animals. Genetic diversity analyses showed a large decline in diversity from the wild-caught stocks to the domesticated stocks. Diversity shifts were noted in both allele numbers per locus corrected for sample size (allelic richness) and heterozygosity, declining from 14.2 to 4.6, and 0.77 to 0.61, respectively. The effective population size ( N e) of a commercial fourth generation domesticated strain, following multiple introductions of wild stocks was estimated at 10, highlighting the bottleneck effects possible within a few generations. Significant differences were noted between all pairs of stocks using F ST analysis (0.042 to 0.160, P < 0.05), with the greatest difference observed between wild animals and a fourth generation domesticated stock sampled from a commercial farm. This study illustrates the rapid loss of genetic diversity and reduction in effective population size that can occur during domestication when rigid genetic management of the stocks is not possible. This study also demonstrates the value of using molecular (microsatellite) marker systems in shrimp breeding programs to monitor genetic diversity and the effective population size.

Attitudes Toward Consumption and Conservation of Tigers in China

A heated debate has recently emerged between tiger farmers and conservationists about the potential consequences of lifting the ban on trade in farmed tiger products in China. This debate has caused unfounded speculation about the extent of the potential market for tiger products. To fill this knowledge gap, we surveyed 1880 residents from a total of six Chinese cities to understand Urban Chinese tiger consumption behavior, knowledge of trade issues and attitudes towards tiger conservation. We found that 43% of respondents had consumed some product alleged to contain tiger parts. Within this user-group, 71% said that they preferred wild products over farmed ones. The two predominant products used were tiger bone plasters (38%) and tiger bone wine (6.4%). 88% of respondents knew that it was illegal to buy or sell tiger products, and 93% agreed that a ban in trade of tiger parts was necessary to conserve wild tigers. These results indicate that while Urban Chinese people are generally supportive of tiger conservation, there is a huge residual demand for tiger products that could resurge if the ban on trade in tiger parts is lifted in China. We suspect that the current supply of the market is predominantly met by fakes or substitutes branded as tiger medicines, but not listing tiger as an ingredient. We suggest that the Traditional Chinese Medicine community should consider re-branding these products as bone-healing medicines in order to reduce the residual demand for real tiger parts over the long-term. The lifting of the current ban on trade in farmed tiger parts may cause a surge in demand for wild tiger parts that consumers say are better. Because of the low input costs associated with poaching, wild-sourced parts would consistently undercut the prices of farmed tigers that could easily be laundered on a legal market. We therefore recommend that the Chinese authorities maintain the ban on trade in tiger parts, and work to improve the enforcement of the existing ban.

Polymorphism of Alternative Splicing of Major Histocompatibility Complex Transcripts in Wild Tiger Salamanders

Alternative splicing (AS) of mRNA transcripts is increasingly recognized as a source of transcriptome diversity. To date, most AS studies have focused either on comparisons across taxa or on intragenomic comparisons across gene families. We generated a novel data set that represents one of the first population genetic comparisons of AS across individuals. In ambystomatid salamanders, AS of the major histocompatibility complex (MHC) class IIbeta gene (Amti-DAB) produces two transcripts, one full-length and one truncated. The full-length transcript is functional, but the truncated transcript is missing the critical beta1 domain that forms half of the peptide binding region in the intact MHC class II molecule. We captured wild salamander larvae (Ambystoma tigrinum tigrinum) and genotyped them at Amti-DAB via DNA sequencing. From these same larvae, we extracted RNA from gill and spleen and evaluated the relative expression level of Amti-DAB in each tissue. Across individuals, 21% of the transcripts were truncated (alternatively spliced), and the absolute level of alternative transcript expression was higher in gill. The high level of nucleotide variation among seven Amti-DAB alleles provides the ability to detect substitutions (or linked DNA polymorphisms) that might have influenced AS. The data reveal no correlation between AS and haplotype, allele, or zygosity. However, indirect evidence (comparative expression patterns across 3 million years of evolution) suggests that the truncated Amti-DAB transcript may be functional and maintained by natural selection.