$x_{n+1} = f_\alpha(x_n,y_n) $
$y_{n+1} = g_\alpha(x_n,y_n)$
where $\alpha$ is a parameter,
$f_\alpha$ and $g_\alpha$ are continuous real valued functions
on a rectangular domain
$\mathcal{R}_\alpha \subset \mathbb{R}^2$ such that
$f_\alpha(x,y)$ is non-decreasing in $x$ and non-increasing in $y$, and $g_\alpha(x, y)$ is non-increasing in $x$ and non-decreasing in $y$.
A unique interior fixed point is assumed
for all values of the parameter $\alpha$.
As an application of the main result for competitive systems a
global period-doubling bifurcation result is obtained for families of
second order difference equations of the type
$x_{n+1} = F_\alpha(x_n, x_{n-1}), \quad n=0,1, \ldots $
where $\alpha$ is a parameter, $F_\alpha:\mathcal{I_\alpha}\times \mathcal{I_\alpha} \rightarrow \mathcal{I_\alpha}$ is a decreasing function in the first variable and increasing in the second variable, and $\mathcal{I_\alpha}$ is a interval in $\mathbb{R}$, and there is a unique interior equilibrium point. Examples of application of the main results are also given.
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