Permanence and Extinction of Periodic Delay Predator-Prey System with Two Predators and Stage Structure for Prey Wei-wei Zheng, Er-dong Han School of Science, Xi’an Polytechnic University, Xi’an, Shaanxi, 710048, PR CHINA (e-mail: zww@nwpu.edu.cn) Abstract – In this paper, a periodic predator-prey delay system with Beddington-DeAngelis and Holling IV functional response is proposed and analyzed, where prey has stage structure and all three species are density dependent. Using the comparison theorem and analytical method, sufficient conditions of the permanence and extinction of the predators and prey species are obtained. In addition, sufficient conditions are derived for the existence of positive periodic solutions of the system. According to the conclusions of the theorems, two examples are given to check the correctness of the main results. here we let R0 ( x1 , x2 , x3 , x4 ) xi 0, i 1,2,3,4 . Keywords – Beddington-DeAngelis functional response, Delay, Extinction, Permanence, Stage Structure According to the analysis of the above, we get the following system (1.3). h1 (t ) x1 (t ) x1 (t ) a(t ) x2 (t ) b(t ) x1 (t ) B(t ) x2 (t 1 ) (t ) x 2 (t ) y1 (t ), 1 1 h ( t ) x ( t ) 2 2 2 x2 (t ) B(t ) x2 (t 1 ) c(t ) x2 (t ) (t ) (t ) x (t ) (t ) y (t ) y2 (t ), 2 2 2 (1.3) y1 (t ) y1 (t ) q1 (t ) p1 (t ) x1 (t 2 ) g1 (t ) y1 (t ) , 1 (t ) x12 (t 2 ) p2 (t ) x2 (t 3 ) y2 (t ) y2 (t ) q2 (t ) (t ) (t ) x (t ) (t ) y (t ) g 2 (t ) y2 (t ) . 2 2 3 2 3 The dynamic behavior of the predator-prey system with delay and stage structure for prey has been long discussed (see [1-4]). Recently, Wang [5] study the model of this type, by using software Maple, the authors got the corresponding numeric results of the conclusions. We can refer to [6-14] to have in-depth understanding of more research achievement of those models. Furthermore, the research concerning the stage structure while being time delays predator-prey periodic systems are quite rare. Indeed, recently, Kar [15], Huang [16] and Chen [17] project those systems on permanence and extinction. To keep the biological variety of ecosystem, the dynamic behavior of biotic population is a significant and comprehensive problem in biomathematics. So it is meaningful to investigate the system (1.3). In the next section, we state the main results of this paper. Sufficient conditions of the permanence and extinction of the system (1.3) are proved in Section III. The conclusions we obtain further promote the analysis technique of Huang [16] and Chen [17]. I. INTRODUCTION The aim of this paper is to investigate the permanence and extinction of the following periodic delay three species predator-prey system with Holling IV and BeddingtonDeAngelis functional response and stage-structure for prey b ( s )ds h1 (t ) x1 (t ) t y1 (t ), x1(t ) a(t ) x2 (t ) b(t ) x1 (t ) a(t 1 )e 1 x2 (t 1 ) 2 1 (t ) x1 (t ) t b ( s )ds h2 (t ) x2 (t ) x2 (t ) a(t 1 )e t1 x2 (t 1 ) c(t ) x22 (t ) y2 (t ), 2 (t ) (t ) x2 (t ) (t ) y2 (t ) (1.1) y(t ) y (t ) q (t ) p1 (t ) x1 (t 2 ) g (t ) y (t ) , 1 1 1 1 1 1 (t ) x12 (t 2 ) p2 (t ) x2 (t 3 ) g 2 (t ) y2 (t ) , y2 (t ) y2 (t ) q2 (t ) 2 (t ) (t ) x2 (t 3 ) (t ) y2 (t 3 ) t x1 (t ) and x2 (t ) denote the densities of immature and mature prey species at time t , respectively; y1 (t ) and y2 (t ) denote the densities of the predators that prey on immature and mature prey at time t , respectively; a(t ), b(t ), c(t ), gi (t ), hi (t ), pi (t ), qi (t ), i (t ), i 1,2, (t ), (t ) are all continuous positive - periodic functions; i , i 1, 2,3 are positive constants. where We can refer to [1-2] to get biological significance of all parameters and assumptions explanation of (1.1). The initial conditions for system (1.1) is as follow xi ( s) i ( s), yi ( s) i ( s) 0, i (0) 0, i (0) 0, i 1, 2, s [ , 0]. (1.2) where max 1 , 2 , 3 , 1 , 2 , 3 , 4 C [ ,0], R0 , 4 4 For the convenient of the following discussion, to a continuous - periodic function f (t ) , we set m( f ) 1 f (t )dt . 0 Meanwhile, we add definition def t B(t ) a(t 1 ) exp b( s)ds . t 1 II. STATEMENT OF THE MAIN RESULTS Theorem 2.1 Suppose that p (t ) x1* (t 2 ) m q1 (t ) 1 0, 1 (t ) x1*2 (t 2 ) (2.2) p2 (t ) x (t 3 ) m q2 (t ) 0, * 2 (t ) (t ) x2 (t 3 ) * * hold, where x1 (t ), x2 (t ) is the unique positive periodic * 2 solution of system (2.1) given by Lemma 2.2 (see [16]). Then system (1.3) is permanent. Theorem 2.2 Assume the condition (2.2) hold, there is at least a positive -periodic solution of system (1.3). Theorem 2.3 Suppose that p (t ) x1* (t 2 ) m q1 (t ) 1 0, 1 (t ) x1*2 (t 2 ) p2 (t ) x2* (t 3 ) m q2 (t ) 0, * 2 (t ) (t ) x2 (t 3 ) (2.3) hold, then any solutions of system (1.3) with initial condition (1.2) satisfies lim yi (t ) 0, i 1, 2 . t every given (0 1), there exists a t for all solutions of system (1.3) with initial condition (1.2). Proof. Let ( x1 , x2 , y1 , y2 ) be a solution of system (1.3) with initial conditions (1.2), so we have x1(t ) a(t ) x2 (t ) b(t ) x1 (t ) B(t ) x2 (t 1 ), 2 x2 (t ) B(t ) x2 (t 1 ) c(t ) x2 (t ). By using Lemma 2.2, the following auxiliary equation: u1(t ) a(t )u2 (t ) b(t )u1 (t ) B(t )u2 (t 1 ), (3.1) 2 u2 (t ) B(t )u2 (t 1 ) c(t )u2 (t ). has a globally asymptotically stable positive - periodic solution x1 (t ), x2 (t ) . Let u1 (t ), u2 (t ) be the solution of On the basis of (3.2) and (3.4), we have xi (t ) xi* (t ) , t T1 . According to the comparison theorem (see [6]), we have (3.2) xi (t ) ui (t )(i 1, 2), t 0 . 0 which is sufficiently small, pi (t ) x (t ) 0. m qi (t ) i (t ) * 1 (3.5) Let M x max xi (t ) , i 1, 2 , we have t[0, ] * lim sup xi (t ) M x , i 1, 2 . t For t T1 , from system (1.3) and (3.5), we can obtain p (t ) x (t 2 ) yi(t ) yi (t ) qi (t ) i i gi (t ) yi (t ) i (t ) p (t ) yi (t ) qi (t ) i ui* (t 2 ) gi (t ) yi (t ) . i (t ) Consider the following equation: p (t ) vi(t ) vi (t ) qi (t ) i ui* (t 2 ) gi (t )vi (t ) . (3.6) i (t ) analysis, there exists a T2 T1 , such that for the above , we have yi (t ) yi* (t ) , t T2 . t[0, ] lim sup yi (t ) M y , i 1, 2 . t To the same argument of Lemma 3.1, we can easily get Lemma 3.2. Lemma 3.2 there exists positive constant ix M x , i 1, 2 , such that lim inf xi (t ) ix , i 1, 2 . t Lemma 3.3 Assumed that (2.2) holds, then there exists two positives constants iy , i 1, 2 , such that any solutions x1 (t ), x2 (t ), y1 (t ), y2 (t ) of system (1.3) with initial condition (1.2) satisfies lim sup yi (t ) iy , i 1, 2 . t (3.7) Proof. Assume that condition (2.2) is establish, there exists a constant 0 that (3.3) Let M y max yi* (t ) , i 1, 2 , then (3.1) with initial condition u1 (0), u2 (0) x1 (0), x2 (0) , By (2.2), there exists a such that (3.4) * lim sup xi (t ) M x , lim sup y (t ) M y , i 1, 2. T1 0, such that ui (t ) xi* (t ) , t T1 . M y , such that * periodic solution yi (t ) 0, i 1, 2 . Similarly to the above We need the Lemma3.1-3.4 to proof Theorem 2.1. Lemma 3.1 There exist positive constants M x and * * From the Lemma 2.2 of [16], (3.6) has a unique - III. PROOF OF THE MAIN RESULTS t * Thus, from the global attractive of x1 (t ), x2 (t ) , for 0 , and 0 1 min xi* (t ) , such t 2 [0, ] m 0 (t ) 0, m 0 (t ) 0 , where (3.8) 0 (t ) q1 (t ) p1 (t ) x1* (t 2 ) 0 1 (t ) x1* (t 2 ) 0 0 (t ) q2 (t ) q1 (t ) 0 , p2 (t ) x2* (t 3 ) 0 q2 (t ) 0 . 2 (t ) (t ) x2* (t 3 ) 0 (t ) 0 Take the equation below with a parameter e 0 into account: h1 (t ) x1(t ) a(t ) x2 (t ) b(t ) 2e x1 (t ) B(t ) x2 (t 1 ), 1 (t ) (3.9) x (t ) B(t ) x (t ) c(t ) 2e h2 (t ) x 2 (t ). 2 2 1 2 2 (t ) By Lemma 2.2, system (3.9) has a unique positive - periodic * * h (t ) x2 (t ) B(t ) x2 (t 1 , ) c(t ) 2e1 2 x22 (t , ). 2 (t ) Let u1 (t ), u2 (t ) be the solution of (3.9), with e e1 and x1 (T6 , ), x2 (T6 , ) , then xi (t , ) ui (t ), i =1,2, t T6 . we let xie (t ) xie (t ) , t T4 . 4 * We have xie (t ) xi (t ) in T4 , T4 , as e 0 .Then, for 0 0 , such that xie (t ) xi* (t ) 0 , t T4 , T4 , 0 e e0 . 4 So, we can get xie* (t ) xi* (t ) xie (t ) xie* (t ) xie* (t ) xi* (t ) * * Since xie (t ), xi (t ) are all xie* (t ) xi* (t ) 0 0 . 2 -periodic, hence , i 1, 2, t 0, 0 e e0 . 2 Choosing a constant e1 (0 e1 e0 , 2e1 0 ) , we have xie* (t ) xi* (t ) 0 2 , there exists T7 0 2 T6 , such that , i 1, 2, t T7 . xi (t , ) ui (t ) xie*1 (t ) 0 , i =1,2, t T7 . 2 Hence, by (3.10), we can obtain xi (t , ) xi* (t ) 0 , i 1, 2, t T7 . * 0 , there exists a sufficiently large T4 T3 , such that 0 * 2 So, we have initial condition xie (0) xi (0), i 1, 2 . Then, for the above 0 ui (t ) xie*1 (t ) solution x1e (t ), x2 e (t ) , which is global attractive. Let x1e (t ), x2e (t ) be the solution of (3.9) with Therefore, by (3.11) and (3.12), for t y1(t , ) (3.10) Assuming (3.7) is false, then there exists R , such 4 that, under the initial condition x1 ( ), x2 ( ), y1 ( ), y2 ( ) , ,0 . We have lim sup yi (t , ) e1 , i 1, 2 . t T4 , such that yi (t , ) 2e1 0 , t T5 . (3.11) By using (3.11), from system (1.3), for all t T6 T5 1 , So, there exists T5 we can obtain h (t ) x1(t ) a(t ) x2 (t , ) b(t ) 2e1 1 x1 (t , ) B(t ) x2 (t 1, ), 1 (t ) (3.12) T7 2 , such that p1 (t ) x1* (t 2 ) 0 y1 (t , ) q1 (t ) g ( t ) 1 0 1 (t ) x1* (t 2 ) 0 0 (t ) y1 (t , ); y2 (t , ) p2 (t ) x2* (t 3 ) 0 y2 (t , ) q2 (t ) g ( t ) 2 0 2 (t ) (t ) x2* (t 3 ) 0 (t ) 0 0 (t ) y2 (t , ). (3.13) 2 to t and Integrating both sides of (3.13) from T7 from T7 3 to t , respectively, so we can get y1 (t , ) y1 (T7 2 , ) exp t T7 2 , i =1,2, t 0 . From the global attractive of x1e1 (t ), x2 e1 (t ) , here y2 (t , ) y2 (T7 3 , ) exp t T7 3 Thus, from (3.11), we obtain (t )dt , 0 (t )dt. 0 yi (t , ) , i 1, 2, t . It is a contradiction of the Lemma 3.1. So the proof of the theorem 3.3 is complete. Lemma 3.4 Under the condition (2.2), there exist positive constants iy , i 1, 2 , such that any solutions of system (1.3) with initial condition (1.2) satisfies lim inf yi (t ) iy , i 1, 2 . t (3.14) Proof of Theorem 2.1 By Lemma 3.2 and 3.3, system (1.3) is uniform weak persistent. Further, from the Lemma 3.1 and 3.4, system (1.3) is persistent. Proof of Theorem 2.2 From the proof of Lemma 3.1- 3.4 in Theorem 2.1, using the same method, we can proof the Theorem 2.2. Here we omit the detail of certificate process. Proof of Theorem 2.3 Actually, by (2.3), for any given positive constant ( 1), there exist 1 0 (0 1 ) and 0 0 , we get the following (3.15). p1 (t ) x1* (t 2 ) 1 m q1 (t ) g1 (t ) m q1 (t ) 0 , 2 2 1 (t ) x1* (t 2 ) 1 Since x1(t ) a(t ) x2 (t ) b(t ) x1 (t ) B(t ) x2 (t 1 ), x2 (t ) B(t ) x2 (t 1 ) c(t ) x22 (t ). (1) 0 , such that xi (t ) x (t ) 1 , t T (1) . * i It follows from (3.15) and t max T 2 , T 3 , (1) (3.16) (3.16) that for (2) p (t ) x (t ) m q1 (t ) 1 1 2 2 g1 (t ) 0 , 1 (t ) x1 (t 2 ) (2) (3.17) ) (i 1, 2) . Otherwise, by (3.17), we have y1 (t ) t h (t ) x (s 2 ) y1 (T (1) 2 )exp (1) q1 (s) 1 1 q1 (s) ds 1 (s) x1 (t 2 ) T 2 y1 (T 2 )exp 0 t T 2 0. (1) (1) . Similarly, we can get y2 (t ) y2 (T (1) 3 )exp 0 t T (1) 3 0, t . as t So we have 0 , which is contradictions. Second, we will prove that yi (t ) exp M ( ) , i 1, 2, t T (2) , (3.18) where p (t ) x (t j ) M ( ) max qi (t ) i 1 gi (t ) , i, j 2,3, i j , t[0, ] i (t ) x1 (t j ) is a bounded constant for 0,1 . Otherwise, then there exists a T (3) T (2) , we can obtain yi (t ) , then there must exists T (4) T (2) , T (3) , such that yi (T (4) ) and yi (t ) , . Let P1 be the nonnegative integer such (3) (4) (3) that T T P1 , T ( P1 1) . From (3.17), we have for t T , T (4) (3) h (t ) x (t ) T (3) y1 (T (3) ) y1 (T (4) )exp (4) q1 (t ) 1 1 2 2 g1 (t ) dt T 1 (t ) x1 (t 2 ) h1 (t ) x1 (t 2 ) g1 (t ) dt q1 (t ) 2 1 (t ) x1 (t 2 ) T (3) h (t ) x (t ) exp (4) d 2 (t ) 1 1 2 2 q(t ) dt 1 (t ) x1 (t 2 ) T P1 exp M ( ) . exp T (4) +P1 T (4) T (3) (4) T P1 We can see that this is a contradiction. Similarly, from the second equation of (3.17), we have exp M ( ) y2 (T (3) ) exp M ( ) . p2 (t ) x2 (t 3 ) m q2 (t ) g 2 (t ) 0 . 2 (t ) (t ) x2 (t 3 ) (2) (1) (2) First, there exists a T max T 2 , T 3 , such that yi (T By the continuity of exp M ( ) p2 (t ) x1* (t 3 ) 1 m q2 (t ) 0 . m q2 (t ) g ( t ) 2 * 2 ( t ) ( t ) x ( t ) 2 1 2 1 For the above 1 , there exists a T yi (T (3) ) exp M ( ) , i 1, 2 . Which is also contradiction, so (3.18) holds. By the random of the parameter , we know yi (t ) 0, i 1,2, t . So we complete the proof of Theorem 2.3. IV. EXAMPLES AND CONCLUSION Example 1 From system (1.3), cause a(t ) 4, b(t ) 2 / 3, c(t ) 9exp0.3 1 exp0.3 , q1(t ) 1/ 4 cos t, q2 (t) 1/ 5 cos t, h1 (t ) 5, h2 (t ) 6, p1 (t ) 2 cos t, p2 (t ) 3 cos t, 1 (t ) 1, 2 (t ) 1 4 1 exp0.3 , (t ) 7 2cos t, (t) 1,1 2 3 0.6, gi (t ), i 1,2 are any arbitrary nonnegative continuous 2 -periodic functions. The above parameters conditions satisfy Theorem 2.1, so system (1.3) is permanent and admits at least a positive 2 - periodic solution. From Fig. 1, we can see that the density restriction of the predators have a major impact on the stability of the predator-prey system. When predator species have no crowding effect, the predator species is at high density; and with crowding effect, the predator species is at low density. Example 2 Assuming that the conditions of example 1 are established. Causing q1 (t ) 5/ 4 cos t , q2 (t ) 1/ 2 cos t , those parameters satisfy the Theorem 2.3. So any positive solution of system (1.3) satisfies lim yi (t ) 0, i 1,2 . t Fig. 2 shows that two predators are extinction and the immature and mature preys are permanent. [2] [3] [4] [5] [6] Fig.1 The growth curve of system (1.3) with initial condition x1 ( ), x2 ( ), y1 ( ), y2 ( ) 1 exp 0.5,0.5,1, 2 , g1(t) 2 sin t, g2 (t) 2 sin t , 0 t 50, 0.6 0. [7] [8] [9] [10] [11] Fig.2 The growth curve of system (1.3) with initial condition x1 ( ), x2 ( ), y1 ( ), y2 ( ) 1 exp0.5,0.5,1,2 ,0 t 50, 0.6 0. From the Theorem 2.1-2.3, we can get a conclusion: the death rate and the density restriction of the two predator population have a great extent influence on the dynamic behavior of the system. 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