지역별 포식압 차이로 인해 나타난 국내 무당개구리 색채와 행동의 지역변이

강창구,Sherratt Tom,김예은,신유진,문종열,강재연,김경민,장이권 한국양서·파충류학회 2018 한국양서·파충류학회 학술대회 Vol.2018 No.07

본 연구에서는 국내에 서식하는 무당개구리 형질의 지역변이를 연구하였다. 지역 변이를 연구하기 위해 2014년 제주지역을 포함한 국내 10곳의 서로 다른 지역에서 무당개구리를 채집하였으며 각 지역에서 채집한 무당개구리의 배와 등의 체색, 행동 적 특성 (발견 장소 및 야간/주간 활동성), 크기를 조사하였다. 조사 결과 가장 큰 차이는 제주개체군과 내륙개체군 사이에서 발견되었으며, 주된 차이점은 배의 체색 과 주간에 발견되는 장소 (낮에 쉬는 행동)에서 나타났다. 제주지역 개체군은 내륙개 체군보다 배의 경고색이 좀 더 어둡고 선명하지 않았으며, 낮에는 주로 잠수하여 숨 어있는 행동을 보였다. 또한 주행성/야행성과 활동성을 비교해 본 결과 제주개체군 은 내륙개체군에 비해 활동성이 현저하게 떨어지는 것을 실험적으로 확인하였다. 내 륙개체군과 제주개체군의 형태/행동의 차이가 내륙과 제주도의 포식압의 차이에서 기인했는지를 추가적으로 검증하기 위해 2016년 여름, 개구리 점토 모형을 이용한 포식압 실험을 수행하였으며 수행 결과 제주지역의 포식압이 내륙지역보다 높은 것 을 확인하였다. 이는 제주도와 내륙지방의 포식압의 차이가 두 지역의 형질분화에 영향을 끼친 요인이라는 것을 시사하고 있다.

Differential predation drives the geographical divergence in multiple traits in aposematic frogs

Kang, C.,Sherratt, T. N.,Kim, Y. E.,Shin, Y.,Moon, J.,Song, U.,Kang, J. Y.,Kim, K.,Jang, Y. Oxford University Press 2017 Behavioral ecology Vol.28 No.4

<P>Prey have evolved a range of traits to enhance their survival against predators. These traits often show geographical variation due to the differences in local predation pressure. To date, there exists ample evidence of the geographical variation in single anti-predator traits such as coloration induced by differential predation. However, predation pressure often induces the shift in a suite of (correlated) prey traits, such as coloration and behavior, rather than a single trait in nature. In this study, we investigated the nature and extent of geographical variation in both color and behavioral traits in the oriental fire-bellied toad, Bombina orientalis, testing whether the frogs experience different predation pressure in different sites and evaluating how this might affect a range of traits associated with predator avoidance. Specifically, we quantified dorsal/ventral coloration, daytime resting place (i.e. the place where each frog was first spotted), and activity levels of natural populations of the frogs in 9 geographically distinct sites distributed across South Korea. We found the clearest differences in these traits between mainland and Jeju Island populations, with Jeju Island frogs exhibiting 1) less bright and less chromatic aposematic ventral coloration than mainland frogs, 2) lower activity during both day and night, and 3) a tendency to rest underwater. Follow-up predation experiments using clay frog models found that frogs in Jeju Island suffer higher predation pressure than mainland frogs, which readily explains the divergence in behavioral and morphological traits among populations.</P>

Body size affects the evolution of hidden colour signals in moths

Kang, Changku,Zahiri, Reza,Sherratt, Thomas N. Royal Society 2017 Proceedings, Biological sciences Vol.284 No.1861

<P>Many cryptic prey have also evolved hidden contrasting colour signals which are displayed to would-be predators. Given that these hidden contrasting signals may confer additional survival benefits to the prey by startling/intimidating predators, it is unclear why they have evolved in some species, but not in others. Here, we have conducted a comparative phylogenetic analysis of the evolution of colour traits in the family Erebidae (Lepidoptera), and found that the hidden contrasting colour signals are more likely to be found in larger species. To understand why this relationship occurs, we present a general mathematical model, demonstrating that selection for a secondary defence such as deimatic display will be stronger in large species when (i) the primary defence (crypsis) is likely to fail as its body size increases and/or (ii) the secondary defence is more effective in large prey. To test the model assumptions, we conducted behavioural experiments using a robotic moth which revealed that survivorship advantages were higher against wild birds when the moth has contrasting hindwings and large size. Collectively, our results suggest that the evolutionary association between large size and hidden contrasting signals has been driven by a combination of the need for a back-up defence and its efficacy.</P>

Flash display increases prey survival against avian predators

Seong-Su No,Thomas N. Sherratt,Chang-Ku Kang 한국응용곤충학회 2022 한국응용곤충학회 학술대회논문집 Vol.2022 No.04

Body size affects the evolution of hidden color signals in insects

Changku Kang,Karl Loeffler-Henry,Thomas N. Sherratt 한국농약과학회 2018 한국농약과학회 학술발표대회 논문집 Vol.2018 No.10

MIMO Channel Capacity and Configuration Selection for Switched Parasitic Antennas

Paramvir Kaur Pal,Robert Simon Sherratt 한국전자통신연구원 2018 ETRI Journal Vol.40 No.2

Multiple‐input multiple‐output (MIMO) systems offer significant enhancements in terms of their data rate and channel capacity compared to traditional systems. However, correlation degrades the system performance and imposes practical limits on the number of antennas that can be incorporated into portable wireless devices. The use of switched parasitic antennas (SPAs) is a possible solution, especially where it is difficult to obtain sufficient signal decorrelation by conventional means. The covariance matrix represents the correlation present in the propagation channel, and has significant impact on the MIMO channel capacity. The results of this work demonstrate a significant improvement in the MIMO channel capacity by using SPA with the knowledge of the covariance matrix for all pattern configurations. By employing the “water‐pouring algorithm” to modify the covariance matrix, the channel capacity is significantly improved compared to traditional systems, which spread transmit power uniformly across all the antennas. A condition number is also proposed as a selection metric to select the optimal pattern configuration for MIMO‐SPAs.

Body size affects the evolution of hidden color signals in insects

Changku Kang,Karl Loeffler-Henry,Thomas N. Sherratt 한국응용곤충학회 2018 한국응용곤충학회 학술대회논문집 Vol.2018 No.10

Deimatic display 는 평상시에는 위장으로 자신을 보호하는 동물들이 포식자에게 위협당하였을 때에만 일시적으로 화려한 경고색을 보여줌으로써 포식자를 놀라게 하여 자신을 보호하는 방어전략이다. 본 연구에서는 3가지의 서로 다른 연구 방법을 이용하여 이 방어전략의 진화에 대해 연구하였으며, 연구의 모델로는 태극나방과 (Erebidae)의 나방을 이용하였다. 첫 번째로 deimatic display 전략이 어떤 종에서 진화하였으며, 이 전략이 동물의 몸 크기와 함께 진화하였는지를 계통수 분석을 이용한 방법으로 연구하였다. 연구 결과 deimatic display 는 몸 크기가 상대적으로 큰 곤충에서 선택적으로 진화하였다는 사실을 발견하였다. 두 번째로 deimatic display 전략이 왜 body size 가 큰 종에서 진화하였는지를 이론적으로 검증하기 위하여 수학적 모델링을 활용, deimatic display 와 몸 크기와의 이론적인 관계를 연구하였다. 이론적 모델링이 시사하는 바는 1) 몸 크기가 클수록 위장이 실패할 확률이 높으며, 2) 몸 크기가 클수록 deimatic display 가 포식자를 위협하는 효과가 클수록 이러한 진화적인 관계가 생성될 수 있다는 점을 발견하였다. 마지막으로 수학적 모델링에서 도출된 결과를 실험적으로 검증하기 위하여 로보틱스 기술을 활용, deimatic display 행동을 보이는 인공나방로봇을 제작하였다. 제작된 인공나방 로봇의 날개크기와 날개색채를 변화시켜가며 나방의 크기가 커질수록 deimatic display 전략이 포식자(조류)를 위협하는데 더 효과적인지를 테스트하였으며, 실험 결과 deimatic display 전략은 나방의 사이즈가 클수록 더 효과적이라는 사실을 입증하였다. 추가 연구 결과 이러한 큰 크기 – 숨겨진 화려한 색채의 관계는 태극나방과 뿐만이 아니라 메뚜기목, 대벌레목, 사마귀목, 그리고 누에나방과(나비목)에서도 발견됨을 확인하였다. 본 연구의 결과는 deimatic display 전략이 큰 크기와 공진화하였음을 보여주며, 이러한 크기-색채 공진화는 deimatic display 전략의 효용성과 밀접한 관련을 가지며 이루어졌다는 사실을 보여준다.

Flash behavior increases prey survival

Loeffler-Henry, K.,Kang, C.,Yip, Y.,Caro, T.,Sherratt, T. N. Oxford University Press 2018 Behavioral ecology Vol.29 No.3

An enhanced fall detection system for elderly person monitoring using consumer home networks

Jin Wang,Zhongqi Zhang,Bin Li,Sungyoung Lee,Sherratt, R. Simon IEEE 2014 IEEE transactions on consumer electronics Vol.60 No.1

<P>Various fall-detection solutions have been previously proposed to create a reliable surveillance system for elderly people with high requirements on accuracy, sensitivity and specificity. In this paper, an enhanced fall detection system is proposed for elderly person monitoring that is based on smart sensors worn on the body and operating through consumer home networks. With treble thresholds, accidental falls can be detected in the home healthcare environment. By utilizing information gathered from an accelerometer, cardiotachometer and smart sensors, the impacts of falls can be logged and distinguished from normal daily activities. The proposed system has been deployed in a prototype system as detailed in this paper. From a test group of 30 healthy participants, it was found that the proposed fall detection system can achieve a high detection accuracy of 97.5%, while the sensitivity and specificity are 96.8% and 98.1% respectively. Therefore, this system can reliably be developed and deployed into a consumer product for use as an elderly person monitoring device with high accuracy and a low false positive rate.</P>

Mobility based energy efficient and multi-sink algorithms for consumer home networks

Jin Wang,Yue Yin,Jianwei Zhang,Sungyoung Lee,Sherratt, R. S. IEEE 2013 IEEE TRANSACTIONS ON CONSUMER ELECTRONICS - Vol.59 No.1

<P>With the fast development of the Internet, wireless communications and semiconductor devices, home networking has received significant attention. Consumer products can collect and transmit various types of data in the home environment. Typical consumer sensors are often equipped with tiny, irreplaceable batteries and it therefore of the utmost importance to design energy efficient algorithms to prolong the home network lifetime and reduce devices going to landfill. Sink mobility is an important technique to improve home network performance including energy consumption, lifetime and end-to-end delay. Also, it can largely mitigate the hot spots near the sink node. The selection of optimal moving trajectory for sink node(s) is an NP-hard problem jointly optimizing routing algorithms with the mobile sink moving strategy is a significant and challenging research issue. The influence of multiple static sink nodes on energy consumption under different scale networks is first studied and an Energy-efficient Multi-sink Clustering Algorithm (EMCA) is proposed and tested. Then, the influence of mobile sink velocity, position and number on network performance is studied and a Mobile-sink based Energy-efficient Clustering Algorithm (MECA) is proposed. Simulation results validate the performance of the proposed two algorithms which can be deployed in a consumer home network environment<SUP>1</SUP>.</P>