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David Buckley

Publications and source records attributed to David Buckley.

12 recordsLinked to original sources
PubMed2026

Comparative Transcriptomic Analyses Identify Candidate Genes for Convergent Reproductive Shifts in a Bimodal Viviparous Amphibian.

Shifts in reproductive mode represent key evolutionary innovations that shape species' life histories and evolutionary trajectories. Species showing bimodal reproductive strategies with multiple independent origins offer a rare opportunity to gain insights into the adaptive processes and mechanisms underlying convergent traits. The fire salamander, Salamandra salamandra, is the only amphibian exhibiting intraspecific variation in reproductive mode across multiple independent reproductive shifts, enabling investigation of the transition between larviparity (females give birth to aquatic larvae) and pueriparity (females give birth to fully developed terrestrial juveniles) within a single species and across different timescales. Pueriparity is an adaptive innovation that skips the aquatic larval stage, allowing individuals to exploit habitats with no available water bodies. The fire salamander is larviparous across most of its range, but pueriparity has evolved independently at least three times: once in the early Pleistocene within S. s. bernardezi in the mountains of northern Spain, and more recently on two land-bridge islands (NW Spain) inhabited by S. s. gallaica. To identify candidate genes associated with these distinct reproductive modes, we compared gene expression profiles of the uterus and oviduct of pregnant females across two independent evolutionary transitions using RNA-sequencing. We detected shared changes in maternal gene expression among pueriparous S. s. bernardezi and S. s. gallaica relative to their larviparous counterparts, in addition to differences unique to each independent evolutionary transition. Functional enrichment analyses indicated that differentially expressed genes were associated with reproductive timing, angiogenesis, and maternal signalling, consistent with the phenotypic differences observed in the uterine environment and embryonic development between the two reproductive modes. This study represents an important first step towards understanding the genomic basis of the evolution of pueriparity in a remarkable bimodal reproductive system, and provides transcriptomic resources and candidate genes for future research into the genomic architecture underlying this poorly understood adaptive trait.

Animals↗
PubMed2024

Adaptive or non-adaptive? Cranial evolution in a radiation of miniaturized day geckos.

Lygodactylus geckos represent a well-documented radiation of miniaturized lizards with diverse life-history traits that are widely distributed in Africa, Madagascar, and South America. The group has diversified into numerous species with high levels of morphological similarity. The evolutionary processes underlying such diversification remain enigmatic, because species live in different ecological biomes, ecoregions and microhabitats, while suggesting strikingly high levels of homoplasy. To underscore this evolutionary pattern, here we explore the shape variation of skull elements (i.e., cranium, jaw and inner ear) using 3D geometric morphometrics and phylogenetic comparative methods on computed tomography scans (CT-scan) of a sample encompassing almost all recognized taxa within Lygodactylus. The results of this work show that skull and inner ear shape variation is low (i.e., there is high overlapping on the morphospace) across geographic regions, macrohabitats and lifestyles, implying extensive homoplasy. Furthermore, we also found a strong influence of allometry shaping cranial variation both at intra and interspecific levels, suggesting a major constraint underlying skull architecture, probably as a consequence of its miniaturization. The remaining variation that is not allometric is independent of phylogeny and ecological adaptation and can probably be interpreted as the result of intrinsic developmental plasticity. This, in turn, supports the interpretation that speciation in this group is largely concordant with a non-adaptive hypothesis, which results mainly from vicariant processes.

Animals↗
PubMed2006

FASD: what types of intervention and rehabilitation are useful?

Fetal alcohol spectrum disorders (FASD) occurs worldwide when children are prenatally exposed to alcohol. This paper discusses recent findings regarding the neuropsychological and behavioral effects of prenatal alcohol exposure and how it impacts the developmental and functional abilities of children with FASD. Specifically, recent research focus has concentrated on studies to elucidate a neurobehavioral phenotype for the alcohol-exposed population. As a result, the FASD field has learned what types of neurobehavioral issues occur most frequently with these children. This paper discusses how that information can be used to inform school assessment, intervention planning, and support. Strategies for functional assessment, individualized planning, structured teaching, and developments in cognitive-behavioral methods are described.

Cognitive Behavioral Therapy↗
PubMed2006

Neurobehavioral characteristics of children with fetal alcohol spectrum disorders in communities from Italy: Preliminary results.

BACKGROUND: There has been considerable effort expended on defining neurobehavioral characteristics of children with fetal alcohol spectrum disorders (FASD). Children with FASD display a range of cognitive deficits and behavioral problems. In this article, we report on the neurobehavioral characteristics of children with FASD in selected communities in Italy. It was expected that both inattentive and hyperactive/impulsive characteristics would discriminate children with FASD from controls and that the groups would also differ on intellectual functioning, language comprehension, and academic skills. METHODS: Eighty-two children, 22 diagnosed with FASD and 60 control children, participated in this study. The children were administered tests of nonverbal reasoning, language comprehension, academic achievement, and behavior. RESULTS: On tests of nonverbal reasoning and language comprehension, the FASD group earned lower scores than did controls. Moreover, on a test of academic achievement the FASD group scored lower. When comparing these 2 groups on disruptive behavioral symptomatology, similar results were obtained, the FASD group showing greater attentional difficulties and hyperactivity/impulsivity behaviors and more overall behavioral problems. Stepwise logistic regression analysis showed that a model containing inattention and error scores on the language comprehension task correctly classified 85% of the participants. Compared with the control group, a significantly greater proportion of children with FASD met the Diagnostic and Statistical Manual of Mental Disorders-fourth edition (DSM-IV) criteria of ADD, inattentive type, as reported by teachers. In contrast, hyperactive symptoms among children with FASD were comparable with the control group. Teachers rated children with FASD as having more inattentive behaviors and as performing lower in academic skills than controls. The association between reported hyperactivity symptoms and achievement scores was nonsignificant for both language and math scores, suggesting that it is not the hyperactivity causing problems, but the child's inattention. CONCLUSIONS: This research indicates that a nonclinic-referred sample of Italian children with FASD display a profile of neurobehavioral functioning consistent with that reported by other researchers. Furthermore, the neurobehavioral characteristic most identified with children diagnosed with FASD was inattention followed by hyperactivity.

Attention Deficit Disorder with Hyperactivity↗
PubMed2006

Epidemiology of FASD in a province in Italy: Prevalence and characteristics of children in a random sample of schools.

BACKGROUND: Accurate estimates of the prevalence and characteristics of fetal alcohol syndrome (FAS) and fetal alcohol spectrum disorders (FASD) in a Western European population are lacking and are of particular interest in settings where the usual pattern of alcohol consumption is thought to be daily drinking with meals. To address these issues, an epidemiology study of FAS and other FASD was undertaken in Italian schools. METHODS: Primary schools (n = 25) in 2 health districts of the Lazio region were randomly selected and recruited for the study. Five hundred forty-three children, 50% of those enrolled in first-grade classes, received parental permission to participate in a 2-tiered, active case ascertainment screening process. Detailed evaluation of children selected in a preliminary screening phase was carried out on those who were small for height, weight, and head circumference and/or referred by teachers for suspected learning and behavioral problems. Detailed evaluation was carried out on each child's: (1) physical growth and dysmorphology, (2) psychological development and behavior, and (3) prenatal exposure to alcohol and other risk factors for FASD via maternal interviews. A group of 67 randomly selected children without FASD from the same classes was utilized as a comparison group. RESULTS: Using 2 denominators for prevalence estimation, a conservative one and a strict sample-based estimate, the prevalence of FAS in this province of Italy was 3.7 to 7.4 per 1,000 children. When cases of partial FAS (PFAS) and a case of alcohol-related neurodevelopmental deficits (ARND) were added to FAS cases, the rate of FASD was 20.3 to 40.5 per 1,000 and estimated at 35 per 1,000 overall or between 2.3 and 4.1% of all children. This exceeds previously published estimates of both FAS and FASD for the western world. Detailed data are presented that demonstrate the utility of the guidelines of the revised Institute of Medicine diagnostic criteria for FASD. Children with FASD are significantly more impaired/affected (p < 0.05) than randomly selected comparison children on all measures of growth deficiency, key facial features of FASD, overall dysmorphology scores, language comprehension, nonverbal IQ, and behavior. Maternal reports of current drinking were significantly higher for mothers of FASD children than comparison mothers, but reported rates of overall drinking during pregnancy were not significantly different. In contrast to expectations, daily drinking among mothers of the comparison group was not common. However, dysmorphology scores of the children were significantly correlated with drinking in the second and third trimesters, drinks per current drinking day, and current drinks per month. Finally, children with the physical features of FASD had lower IQs; nonverbal IQ was significantly correlated with head circumference and negatively correlated with overall dysmorphology score, smooth philtrum, and several other facial and physical anomalies characteristic of FAS. CONCLUSIONS: Using careful measures of ascertainment in a primary school setting, these results provide relatively high estimates of the prevalence of FASD and raise the question of whether FASD is more common in the western world than previously estimated.

Abnormalities, Drug-Induced↗
PubMed2006

Comparison of motor delays in young children with fetal alcohol syndrome to those with prenatal alcohol exposure and with no prenatal alcohol exposure.

BACKGROUND: Researchers are increasingly considering the importance of motor functioning of children with fetal alcohol spectrum disorder (FASD). The purpose of this study was to assess the motor development of young children with fetal alcohol syndrome (FAS) to determine the presence and degree of delay in their motor skills and to compare their motor development with that of matched children without FAS. METHODS: The motor development of 14 children ages 20 to 68 months identified with FAS was assessed using the Vineland Adaptive Behavior Scales (VABS). In addition, 2 comparison groups were utilized. Eleven of the children with FAS were matched for chronological age, gender, ethnicity, and communication age to: (1) 11 children with prenatal alcohol exposure who did not have FAS and (2) 11 matched children without any reported prenatal alcohol exposure. The motor scores on the VABS were compared among the 3 groups. RESULTS: Most of the young children with FAS in this study showed clinically important delays in their motor development as measured on the VABS Motor Domain, and their fine motor skills were significantly more delayed than their gross motor skills. In the group comparisons, the young children with FAS had significantly lower Motor Domain standard (MotorSS) scores than the children not exposed to alcohol prenatally. They also had significantly lower Fine Motor Developmental Quotients than the children in both the other groups. No significant group differences were found in gross motor scores. For MotorSS scores and Fine Motor Developmental Quotients, the means and standard errors indicated a continuum in the scores from FAS to prenatal alcohol exposure to nonexposure. CONCLUSIONS: These findings strongly suggest that all young children with FAS should receive complete developmental evaluations that include assessment of their motor functioning, to identify problem areas and provide access to developmental intervention programs that target deficit areas such as fine motor skills. Fine motor delays in children with FAS may be related to specific neurobehavioral deficits that affect fine motor skills. The findings support the concept of an FASD continuum in some areas of motor development.

Adaptation, Psychological↗
PubMed2006

Educational planning for children with fetal alcohol syndrome.

It has now been thirty-two years since Jones and Smith first identified fetal alcohol syndrome (FAS) in the United States. Since then, numerous epidemiology studies have been conducted to determine prevalence rates of this disorder. More recently, the research focus has concentrated on studies to elucidate a neurobehavioral phenotype for the alcohol-exposed population. As a result, the FAS field has learned what types of neurobehavioral issues occur most frequently with these children. This paper discusses the results of neurobehavioral research with alcohol exposed children and how that information can be used to inform school assessment, intervention planning, and support.

Adult↗
PubMed2005

The effect of binocular and monocular distractors on saccades in participants with normal binocular vision.

We tested the effect of visual distractors presented monocularly and binocularly on saccade latency and accuracy to determine whether differences occur in saccadic planning with binocular or monocular visual input. For five participants with normal binocular single vision (BSV), saccade latency and accuracy were compared with distractors presented to the dominant eye, non-dominant eye or to both eyes. Eye movements of the dominant eye were recorded using a Skalar infra-red recorder. In the presence of normal BSV, the effect of distractors is significantly larger for saccade latency and accuracy with binocular distractor presentation than for monocular presentations, with no difference between distrators presented to the dominant or non-dominant eye. The implications of these results are discussed with regard to saccade programming.

Adult↗
PubMed2004

The effects of ageing on stereopsis. A VEP study.

Differences in brain activation between young (n = 11, ages 21-35) and elderly (n = 8, ages 70-84) healthy participants were studied using visual evoked potentials (VEPs) to different kinds of computer generated random-dot patterns. The main stimulus of interest was a 2 x 2 array of rectangles whose rectangles moved to and fro in depth. Control conditions were similar 2 x 2 arrays, one with side-to-side lateral motion (LM) of the rectangles, and one a stationary baseline condition. The third non-stereo stimulus was an expanding field of small dots in radial motion (RM). Significant stereo related activation was found in both age groups. The stereo VEPs showed a longer latency of depth reversal triggered VEP peaks compared to control LM VEPs. The amplitudes of LM VEPs were larger than the baseline VEPs. Age-related differences were found not only in stereo but also in the other conditions. Thus the latency of early VEP peaks was shorter and their amplitude higher in the elderly for LM and baseline conditions, and the younger participants showed significantly higher activation in the later VEP peaks of all conditions. Our main finding is no evidence for age related stereo specific effects in brain activation, but instead more general and subtle changes that affect widely different visual stimulus conditions.

Adult↗
PubMed2002

Accommodation to large disparity stereograms.

PURPOSE: The purpose of this study was to test whether observers would show accommodation changes to depth depicted in large disparity stereograms and whether the amount of accommodation was related to the amount of depth seen in the stereograms. Previous studies have shown small accommodation changes to depth depicted in stereograms. We tested a larger range of depths than previously investigated and also asked observers to judge the depth depicted in the stereogram, because a previous study had suggested that this might be an important factor. METHODS: All our observers had emmetropia. Accommodation was measured with a Canon Autoref R-1autorefractor as an observer viewed a depthful 4-by-4 cm planar target set against a 20-by-20 cm planar background 57 cm from the observer. The target was presented at a range of depths, -8 to +8 cm, either in stereogram stimuli or real stimuli. Each observer also made depth judgments of stereogram targets, after training with real targets. We also recorded the time taken for each observer to discern the depicted depths in stereograms. RESULTS: The accommodation shown by all observers (n = 9) to stereogram targets was significant but was on average about 60% of that predicted. There were individual differences in the accommodation an observer showed to stereogram targets, but this was not related to the amount of depth the observer saw in the stereogram. CONCLUSIONS: Accommodation changes did occur to stereogram targets, but these were generally less than predicted and also less than those shown for real targets. Possible reasons for these findings and the implications for the use of stereograms in clinical tests are discussed.

Accommodation, Ocular↗
PubMedDate not supplied

Heterochrony, cannibalism, and the evolution of viviparity in Salamandra salamandra.

The way in which novelties that lead to macroevolutionary events originate is a major question in evolutionary biology, and one that can be addressed using the fire salamander (Salamandra salamandra) as a model system. It is exceptional among amphibians in displaying intraspecific diversity of reproductive strategies. In S. salamandra, two distinct modes of reproduction co-occur: the common mode, ovoviviparity (females giving birth to many small larvae), and a phylogenetically derived reproductive strategy, viviparity (females producing only a few large, fully metamorphosed juveniles, which are nourished maternally). We examine the relationship between heterochronic modifications of the ontogeny and the evolution of the new reproductive mode in the fire salamander. The in vitro development of embryos of ovoviviparous and viviparous salamanders from fertilization to metamorphosis is compared, highlighting the key events that distinguish the two modes of reproduction. We identify the heterochronic events that, together with the intrauterine cannibalistic behavior, characterize the derived viviparous reproductive strategy. The ways in which evolutionary novelties can arise by modification of developmental programs can be studied in S. salamandra. Moreover, the variation in reproductive modes and the associated variation of sequences of development occur in neighboring, conspecific populations. Thus, S. salamandra is a unique biological system in which evolutionary developmental research questions can be addressed at the level of populations.

Animals↗